7. Evaluate the Effect of Reduced Class Size on
Behavior or Achievement

This kind of project requires two kinds of evaluation:

1. A formative evaluation to determine if class size(s) have been significantly reduced.

2. A summative evaluation to determine if the reduction in class size has resulted in fewer disciplinary incidents or improved student achievement scores (or both).

I  Formative Evaluation

The task here is to determine if there has been a significant reduction in class size. This is not something that can be taken for granted. You will need to document the fact that the number of pupils in the classes you are studying is in fact fewer than was previously the case. It is important to remember that class size is not the same as student/teacher ratio. The latter usually includes non-teaching staff.

It is essential to establish that significant class-size reduction has occurred before undertaking a summative, impact, or outcome evaluation. It makes no sense to evaluate the effectiveness of a program that does not exist-even though we regrettably see many instances of this.

II  Summative Evaluation

The two basic questions here are:

>Has there been a reduction in disciplinary incidents and/or an improvement on some measure of student achievement?

>Can any changes that have occurred be confidently attributed to reduced class size rather than other factors?

There are two preferred evaluation designs for answering these questions:

(1) Administer pre- and post- achievement tests (and/or collect discipline-incident data) on both a group of students who have attended smaller classes and a comparable control group of students who haven't. If the gains in achievement or the reductions in disciplinary incidents in the small-class group are statistically and educationally greater than those of the control group, you can confidently conclude that these gains were the result of reduced class size. Simply administering pre- and post-tests to the treatment or program group without a control group will not do. Achievement scores may have increased and disciplinary incidents may have declined because of other conditions or factors besides class-size reduction. For comparison, you need some measure of change under the conditions of non-treatment. This is provided by the control group. (See the section on An Example of the Most Common Pitfall in Evaluating Education Programs in the Short Course on Evaluation Basics.)

(2) As an alternative, if a control group is not available, you can use what is known as the interrupted time-series design. If test scores or disciplinary data are available for several years or periods prior to the reduction in class size, and there is a marked improvement in these scores immediately following the reduction that is sustained in following years or periods, you can confidently conclude that the improvements were the result of the new program.

For more information on these two designs, see the section on Alternative Summative Evaluation Methods in the Short Course on Evaluation Basics, and references 1 (Campbell), 4 (Cook & Campbell), and 8 (Rossi & Freeman) in the Evaluation References.

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