The Basics:

The school performance scores displayed in this chart were downloaded in March 2019 from the Texas Education Agency's website (here). Those interested in reviewing reports on individual schools can search here. These agencies make such data available to the public as a matter of policy. The Education Consumers Foundation simply displays that which is publicly available in a consumer-friendly way. Economically disadvantaged data displayed in this chart was downloaded from the Texas Education Agency's website (here).

About the Chart
Learning to read is one of the highest priorities of elementary school. Students who do not master reading are at a substantially higher risk of academic failure in high school. 

As indicated by this chart, reading proficiency is correlated with economic disadvantage.  Schools with higher percentages of economically advantaged students have higher proficiency rates in reading.  The exceptions, however, are important.  Schools with the same proportion of disadvantaged students may differ by 50-60 points in proficiency rate.
 
Students from economically disadvantaged households are frequently a grade-level or more behind their more advantaged peers at entry to preschool or kindergarten.  Plainly, schools are not responsible for these differences, but they are responsible for providing the educational experiences that will enable disadvantaged and other struggling readers to catch up with their peers.  Unfortunately, teaching methodologies that can close these gaps are little used.  Users interested in learning more about early reading instruction alternatives should go here.

Improving third grade reading proficiency rates is arguably the single most cost-effective change a school can make to improve overall achievement outcomes. Better readers gain greater benefit from school. Users interested in more informationon improving outcomes are strongly encouraged to read "Annual Growth, Catch-Up Growth" by Lynn Fielding.

Reading the Chart
The horizontal scale (x-axis) represents the percentage of a school's students who are identified by the Texas Education Agency as members of a low income family. “Low income families” are defined as such by participation in the federal Free and Reduced Lunch program or other form of public assistance (see here).

The vertical scale (y-axis) represents the percentage of a school's third grade students who meet or exceed reading standards --as defined by the Texas Education Agency. These are the students who have mastered reading and are prepared to advance to the next grade.