The Ethnic Diversity Index is intended to measure how much "diversity" or "variety" a school or district has among the ethnic groups in its student population. More specifically, the Index reflects how evenly distributed these students are among the race/ethnicity categories reported to the California Department of Education.
The more evenly distributed the student body, the higher the number. For example, a school that had exactly 1/8th of its students in each of the eight categories* would have an Ethnic Diversity Index of 100, and a school where all of the students are the same ethnicity would have an index of 0. In reality, of course, no school has an index of 100 (although a few have diversity indices of 0). Currently the highest index for a school is 76.
Two schools with the same Ethnic Diversity Index may have student bodies with quite different ethnic compositions. For example, a school with a student population that is half Hispanic/Latino and half Native American would have the same index as a school with a student population that is half Filipino and half African American because both schools have only two ethnic groups in their student populations that are roughly evenly divided at the school. The Index does not single out and give more weight to one ethnic group over another.
The Ethnic Diversity Index is not meant to indicate the magnitude of the challenges faced by a given school or district based upon student characteristics. Many student population characteristics present challenges: family socioeconomic conditions, parent education level, number of different native languages spoken, extent of community involvement, and others. This Index does not incorporate those other important student characteristics. Ed-Data viewers wanting to gauge school challenges should also consider the unduplicated pupil count of English Learners, students eligible for free and reduced-price meals (FRPM), and foster youth. The FRPM counts include homeless and migrant students.
That said, the Ethnic Diversity Index does show an important characteristic about a school's or district's student population (taking into account, for example, how many ethnic groups are part of the campus and community) that is not easily evident without the index. It can be a useful piece of information for understanding a school or district.
*Note: There are actually nine categories reported, but the "none reported" category is factored out of the Ethnic Diversity Index calculation.
There are eight Ethnic Groups plus None Reported, which is factored out from the calculation.
D(8) = SQRT(((FractionAfricanAm-(1/8))2) + ((FractionAmIndian-(1/8))2) + ((FractionAsian-(1/8))2) + ((FractionHispanic-(1/8))2)+ ((FractionFilipino-(1/8))2) + ((FractionPacIslander-(1/8))2) + ((FractionWhite-(1/8))2) + ((Fraction2orMore-(1/8))2))
C1 = 100
C2 = -100*SQRT(8*(8-1))/(8-1) = -100*SQRT(56)/7 = -106.90449
EDI = C1 + (C2*D(8)) = 100 + (-106.90449*D(8))
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