Exploring Class Size in Michigan
There is a substantial body of research linking class size to student achievement. Unfortunately, the most commonly reported measure of class size, the student-teacher ratio, does not actually measure the number of students in any particular classroom. The student-teacher ratio systematically understates class size because it includes specialized teachers who do not preside over a traditional classroom. Moreover, the typical student-teacher ratio measure does not allow one to look separately by subject or grade level, or to identify particularly large classes.
Using student-level transcript data collected from individual districts by the State of Michigan, we have calculated actual class size measures for schools across the state. The recently released policy brief describes our findings statewide, including how class size varies with student race, poverty, grade and subject. The Michigan Class Size Comparison Tool below allows you to compare class sizes across districts throughout the state of Michigan.
Source of Data
The underlying data utilized in our analysis is provided by the Michigan Center for Educational Performance and Information's Student Data Link. The data support requirements of the America Competes Act as part of the State Fiscal Stabilization Fund, as well as the state's accountability scorecard calculations.
If you cannot find your district, or you believe the number of students presented for the district is incorrect, read the explanation below.
The statistics presented here are based on student-level transcript data for the academic year 2014-15 collected by the Michigan Department of Education from school districts throughout the state.
Note that not all school districts are represented in the statistics we present here. We include only schools that serve students in grades 1, 7 or 9, and we do not include data from a school x grade if there were fewer than 10 students in the grade in that school during the 2014-15 academic year based on the enrollment files maintained by the State of Michigan. We exclude special needs schools as well as a handful of schools with missing data. We do not include data on virtual classes or classes that exclusively serve students classified as Limited English Proficient or students who receive special education services. Individual students were excluded from the analysis if their transcript data did not include the data necessary to allow us to identify the student’s classroom. After the initial calculation of class size, we drop classes that appear to have fewer than 5 or greater than 55 students because we believe that these cases are most likely data errors.
In some cases entire grades within a school were excluded because there were no classrooms within the school in the chosen grade that met the inclusion criteria. Likewise, an entire district might not be represented in this analysis if there were no grades in any school in the district with sufficient data. Finally, if fewer than 50% of students in a particular grade in district could not be included in our analysis, we set the class size data for that district x grade to missing because we are not confident that it provides an accurate representation of class size for that district.
In interpreting the class size statistics presented here, please note that they are based on all students in a class, including students in grades other than grades 1, 7 and 9 as well as students who attended the school for only part of the year. For example, if a classroom contained students in grades 1 and 2, the class size we report would include the second grade students. And if several of these first and/or second graders transferred out of the school partway through the year, they would nonetheless be included in the class size statistics. In contrast, the statistics that report the number of students in a district x grade include only students actually in that grade, and only counts students who attended the school for the majority of the school year. Lastly, the data used for this analysis does not include information on teaching assistants and/or school aides. Thus, it is possible that some of the large classes in our analysis include more than one adult in a teaching capacity.
For additional information on the data and sample construction, please see the appendices.