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Small class sizes for improving student achievement in primary and secondary schools

Additional Info

  • Authors: Trine Filges, Christoffer Scavenius Sonne-Schmidt, Bjørn Christian Viinholt Nielsen
  • Published date: 2018-10-11
  • Coordinating group(s): Education
  • Type of document: Review, Plain language summary
  • Title: Small class sizes for improving student achievement in primary and secondary schools
  • Library Image: Library Image
  • See the full review: https://onlinelibrary.wiley.com/doi/10.4073/csr.2018.10
  • Records available in: English, Spanish
  • English:

    PLAIN LANGUAGE SUMMARY

    Small class size has at best a small effect on academic achievement, and may harm some students

    Reducing class size is seen as a way of improving student performance. But larger class sizes help control education budgets. The evidence suggests at best a small effect on reading achievement. There is a negative, but statistically insignificant, effect on mathematics, so it cannot be ruled out that some children may be adversely affected.

    What is this review about?

    Increasing class size is one of the key variables that policy makers can use to control spending on education.

    But the consensus among many in education research is that smaller classes are effective in improving student achievement which has led to a policy of class size reductions in a number of U.S. states, the United Kingdom, and the Netherlands. This policy is disputed by those who argue that the effects of class size reduction are only modest and that there are other more cost-effective strategies for improving educational standards.

    Despite the important policy and practice implications of the topic, the research literature on the educational effects of class-size differences has not been clear.

    This review systematically reports findings from relevant studies that measure the effects of class size on academic achievement.

    What is the aim of this review?

    This Campbell systematic review examines the impact of class size on academic achievement. The review summarises findings from 148 reports from 41 countries. Ten studies were included in the meta-analysis.

    What studies are included?

    Included studies concerned children in grades kindergarten to 12 (or the equivalent in European countries) in general education. The primary focus was on measures of academic achievement. All study designs that used a well-defined control group were eligible for inclusion.

    A total of 127 studies, consisting of 148 papers, met the inclusion criteria. These 127 studies analysed 55 different populations from 41 different countries. A large number of studies (45) analysed data from the Student Teacher Achievement Ratio (STAR) experiment which was for class size reduction in grade K-3 in the US in the eighties. However only ten studies, including four of the STAR programme, could be included in the meta-analysis.

    What are the main results in this review?

    Overall, the evidence suggests at best a small effect on reading achievement. There is a negative, but statistically insignificant, effect on mathematics.

    For the non-STAR studies the primary study effect sizes for reading were close to zero but the weighted average was positive and statistically significant. There was some inconsistency in the direction of the primary study effect sizes for mathematics and the weighted average effect was negative and statistically non-significant.

    The STAR results are more positive, but do not change the overall finding. All reported results from the studies analysing STAR data indicated a positive effect of smaller class sizes for both reading and maths, but the average effects are small.

    What do the findings in this review mean?

    There is some evidence to suggest that there is an effect of reducing class size on reading achievement, although the effect is very small. There is no significant effect on mathematics achievement, though the average is negative meaning a possible adverse impact on some students cannot be ruled out.

    The overall reading effect corresponds to a 53 per cent chance that a randomly selected score of a student from the treated population of small classes is greater than the score of a randomly selected student from the comparison population of larger classes. This is a very small effect.

    Class size reduction is costly. The available evidence points to no or only very small effect sizes of small classes in comparison to larger classes. Moreover, we cannot rule out the possibility that small classes may be counterproductive for some students. It is therefore crucial to know more about the relationship between class size and achievement in order to determine where money is best allocated.

    How up-to-date is this review?

    The review authors searched for studies published up to February 2017.

  • Spanish:

    RESUMEN EN LENGUAJE SENCILLO

    Las clases pequeñas tienen, en el mejor de los casos, un efecto leve en el rendimiento académico y pueden perjudicar a algunos estudiantes

    Se piensa que las clases con menos alumnos mejoran su rendimiento. Pero las clases más grandes ayudan a controlar los presupuestos educativos. La evidencia sugiere, en el mejor de los casos, un efecto leve sobre la comprensión lectora. Existe un efecto negativo, aunque estadísticamente insignificante, en matemáticas, por lo que no se puede descartar que algunos niños se vean afectados negativamente

    ¿Cuál es el tema que trata esta revisión?

    Aumentar el tamaño de las clases es una de las variables clave que los formuladores de políticas pueden utilizar para controlar el gasto en educación.

    Pero existe una opinión generalizada en la investigación sobre educación de que las clases más pequeñas son efectivas para mejorar el rendimiento estudiantil, lo que ha llevado a una política de reducción del tamaño de las clases en varios estados de EE.UU., en el Reino Unido y en Holanda. Esta política es cuestionada por aquellos que argumentan que los efectos de la reducción de tamaño de la clase son apenas modestos, y que existen otras estrategias más rentables para mejorar el nivel educativo.

    A pesar de las importantes implicancias políticas y prácticas del tema, la literatura de investigación que versa sobre los efectos en la educación de las diferencias en el tamaño de las clases no ha sido clara.

    Esta revisión informa sistemáticamente acerca de los resultados de estudios relevantes que miden los efectos del tamaño de la clase sobre el rendimiento académico.

    ¿Cuál es el objetivo de esta revisión?

    Esta revisión sistemática Campbell examina el impacto del tamaño de la clase sobre el rendimiento académico. La revisión resume los hallazgos de 148 informes de 41 países. Diez de los estudios fueron incluidos en el metaanálisis.

    ¿Qué estudios se incluyen?

    Los estudios incluidos involucraron a niños entre kindergarten hasta el doceavo grado (o su equivalente en países europeos) de la educación general. El enfoque principal se centró en las mediciones del rendimiento académico. Todos los diseños de estudio que utilizaron un grupo de control bien definido se consideraron elegibles para ser incluidos.

    Un total de 127 estudios, que constaban de 148 artículos, cumplieron con los criterios de inclusión. Estos 127 estudios analizaron 55 poblaciones diferentes en 41 países distintos. Varios de los estudios (45) analizaron los datos del experimento STAR, focalizado en la reducción del tamaño de clases en el grado K-3 estadounidense.

    ¿Cuáles son los principales hallazgos de esta revisión?

    Para los cinco estudios no relacionados con STAR, la magnitud del efecto del estudio principal en cuanto a lectura se encuentra en el rango -0.08 a 0.14. Tres de los efectos a nivel de estudio no fueron estadísticamente significativos, y el efecto promedio corresponde a 0.11, lo cual se considera leve. La magnitud del efecto en cuanto a matemáticas se ubicó entre -0.41 y 0.11. El efecto promedio ponderado fue negativo y estadísticamente no significativo.

    Los resultados de STAR son más positivos. Los resultados de los cuatro estudios que analizaron los datos de STAR informaron un efecto positivo en las clases más pequeñas. El efecto en la lectura tuvo una variación entre 0.17 y 0.34 puntos, y para matemáticas entre 0.15 y 0.33. Los promedios en ambos casos son pequeños.

    ¿Qué significan los resultados de esta revisión?

    Cierta evidencia sugiere que una reducción en el tamaño de la clase afecta la comprensión lectora, aunque de forma leve. No existe un efecto significativo sobre el rendimiento en matemáticas, aunque el promedio es negativo, lo cual significa que no se puede descartar un posible impacto adverso sobre algunos estudiantes.

    El efecto general sobre la lectura conlleva un 53% de probabilidad de que un puntaje seleccionado aleatoriamente entre alumnos de la población tratada con clases pequeñas sea mayor que el puntaje seleccionado aleatoriamente entre alumnos de la población de comparación con clases más grandes. Este efecto es muy leve.

    Reducir el tamaño de la clase resulta caro. La evidencia disponible apunta a que los efectos de las clases pequeñas en comparación con clases más grandes son nulos o muy leves. Además, no podemos descartar la posibilidad de que las clases pequeñas sean contraproducentes para algunos alumnos. Por lo tanto, es fundamental saber más acerca de la relación entre el tamaño de la clase y el rendimiento para determinar cómo llevar a cabo una mejor asignación de los recursos financieros.

    ¿Cuán actualizada es esta revisión?

    Los autores de la revisión buscaron estudios publicados hasta el Febrero 2017. Esta revisión sistemática Campbell fue publicada en 2018.

Select language:

PLAIN LANGUAGE SUMMARY

Small class size has at best a small effect on academic achievement, and may harm some students

Reducing class size is seen as a way of improving student performance. But larger class sizes help control education budgets. The evidence suggests at best a small effect on reading achievement. There is a negative, but statistically insignificant, effect on mathematics, so it cannot be ruled out that some children may be adversely affected.

What is this review about?

Increasing class size is one of the key variables that policy makers can use to control spending on education.

But the consensus among many in education research is that smaller classes are effective in improving student achievement which has led to a policy of class size reductions in a number of U.S. states, the United Kingdom, and the Netherlands. This policy is disputed by those who argue that the effects of class size reduction are only modest and that there are other more cost-effective strategies for improving educational standards.

Despite the important policy and practice implications of the topic, the research literature on the educational effects of class-size differences has not been clear.

This review systematically reports findings from relevant studies that measure the effects of class size on academic achievement.

What is the aim of this review?

This Campbell systematic review examines the impact of class size on academic achievement. The review summarises findings from 148 reports from 41 countries. Ten studies were included in the meta-analysis.

What studies are included?

Included studies concerned children in grades kindergarten to 12 (or the equivalent in European countries) in general education. The primary focus was on measures of academic achievement. All study designs that used a well-defined control group were eligible for inclusion.

A total of 127 studies, consisting of 148 papers, met the inclusion criteria. These 127 studies analysed 55 different populations from 41 different countries. A large number of studies (45) analysed data from the Student Teacher Achievement Ratio (STAR) experiment which was for class size reduction in grade K-3 in the US in the eighties. However only ten studies, including four of the STAR programme, could be included in the meta-analysis.

What are the main results in this review?

Overall, the evidence suggests at best a small effect on reading achievement. There is a negative, but statistically insignificant, effect on mathematics.

For the non-STAR studies the primary study effect sizes for reading were close to zero but the weighted average was positive and statistically significant. There was some inconsistency in the direction of the primary study effect sizes for mathematics and the weighted average effect was negative and statistically non-significant.

The STAR results are more positive, but do not change the overall finding. All reported results from the studies analysing STAR data indicated a positive effect of smaller class sizes for both reading and maths, but the average effects are small.

What do the findings in this review mean?

There is some evidence to suggest that there is an effect of reducing class size on reading achievement, although the effect is very small. There is no significant effect on mathematics achievement, though the average is negative meaning a possible adverse impact on some students cannot be ruled out.

The overall reading effect corresponds to a 53 per cent chance that a randomly selected score of a student from the treated population of small classes is greater than the score of a randomly selected student from the comparison population of larger classes. This is a very small effect.

Class size reduction is costly. The available evidence points to no or only very small effect sizes of small classes in comparison to larger classes. Moreover, we cannot rule out the possibility that small classes may be counterproductive for some students. It is therefore crucial to know more about the relationship between class size and achievement in order to determine where money is best allocated.

How up-to-date is this review?

The review authors searched for studies published up to February 2017.

Library Image

See the full review

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