Atlanta Public Schools has the most diverse portfolio of schools in the state. We have schools in some of the wealthiest neighborhoods in Georgia and schools in some of the poorest. The graph below shows that these schools have very different achievement levels:



The challenge index measures the percentage of students who are either directly certified1 for free lunch or English language learners. Only about 3% of APS students are English Language Learners so for most schools the Challenge Index can be thought of approximately as a measure of poverty.

Notice the strong relationship between the Challenge Index and average test scores. The Challenge Index explains about 91% of the variance in elementary school average test scores. Remember that this is a relationship between school averages. There is much more variation at the individual student level.

Comparing schools with similar challenge indices is helpful for understanding school performance. A school that is above the trend line has higher test scores than other schools with a similar level of poverty.

The next graph uses the same data as above, but is color-coded by the percentage of students who demonstrated typical or high growth. We see that schools with high growth (blue color-coding) tend to be above the trend line, while schools with low growth (orange/brown color-coding) tend to be below the trend line. But there are some exceptions. This could be due to a few different reasons:

1. The growth data only measures grades four and five, but a student’s achievement is also affected by the instruction they experienced in grades k-3. A school with a great instruction in grades k-3, but below average instruction in grades 4 and 5 could still be above the trend line. 2. This year’s growth could be different from growth in previous years. For example, Thomasville had above average growth in 2017, but several years of below-average growth before that, so one good year was not enough to raise the school above the trend line. 3. The challenge index is not a perfect measure of resources. The challenge index is mostly a binary measure of poverty and might not capture additional variation, such as the difference between middle income and very wealthy, or poor and very poor.

The y-axis for these graphs uses average Milestones NCE score, which is similar to average test score, but converted to a common scale to average across grades and subjects. We display average test scores on this graph because an average is a more accurate summary than reporting the percentage of students above a cut score. However, percentages are also useful for understanding performance, so we allow the user to change the y-axis with the performance metric filter on the left.

Notice how the distribution changes for different metrics. The graph below shows the percentage of students scoring developing and above on the Milestones. (See here for an explanation of Milestones achievement levels.) This metric emphasizes the difference in test scores between our high poverty schools, while our low-poverty schools show similar performance.



The next graph shows the percentage of students scoring distinguished. Now the test score differences between low-poverty schools is emphasized, while the high poverty schools show similar performance.



Finally, we also have this data for End of Course tests, which shows comparisons for high schools and eighth grade advanced math students.

To view other measures of school performance, see our recent post on student growth percentiles, or our school profiles. If you have questions about this data, feel free to contact us using the form on the About page. If you like this post, and would like to know about similar posts, please subscribe to the blog.

1. A student is directly certified for free lunch if their household receives state anti-poverty aid (SNAP or TANF) or if the student is homeless, an unaccompanied youth, a foster child, or a migrant. This measure is used instead of the more general “free and reduced lunch” because many APS schools use the CEP option for whole-school free and reduced lunch.