This story from the Houston Chronicle doesn’t really address that, but does give more details on this epidemic:
Only 67% of eligible Texans graduated in ’03, study says
Education Week report contradicts TEA’s 83% claim
— reported by the Houston ChronicleOnly two-thirds of Texas’ eligible students earned a high school diploma in 2002-03, 16 percentage points lower than the 83 percent graduation rate touted by the Texas Education Agency that year, according to a study released Tuesday by Education Week magazine.
[snip]
Texas students are 20 percent more likely to live in poverty and 60 percent more likely to be English-language learners than national averages, according to the report.
The study, Diplomas Count, shows that 1.2 million U.S. students failed to graduate with their classmates in 2006.
[snip]
Most dropouts leave school in the ninth grade, including 40 percent of dropouts in low-income districts including Houston, officials said.
Texas measured up well in other standards.
The state requires students to earn 22 credits to graduate, slightly higher than the national average.
It’s one of 23 states that requires student to pass an exit-exam to graduate, and Texas also requires students to attend school until they’re 18, a year longer than the national average.