Paul Krugman and Kevin Drum wisely argue that we can't blame Texas' nearly non-existent teachers unions for problems in Texas' public schools, but taking a look at the data I'm not sure there's even much of a problem to blame anyone for.
Consider the 2011 NAEP math scores for 8th graders. The average score for Texans eligible for subsidized school lunches is 281 against a national average of 269. For kids not eligible for subsidies the national average is 295 and in Texas it's 301. For 8th grade reading, Texas is basically average. The national average for low-income kids is 251 and for Texas low-income kids it's 253. For non-subsidized Texans it's 274 and for the nationally non-subsidized population it's 275. If you break it out by race, Texas' white 8th graders read slightly better than the national average for white kids. Their black 8th graders read slightly better than the national average for black kids. And Texas' Hispanic 8th graders read slightly better than the national average for Latino kids.
Now of course overall Texas' test scores aren't so hot. The state has a very high poverty rate and a lot of kids growing up in Spanish-dominant households. But once you apply any kind of plausible demographic controls, Texas school performance seems good. If you want to worry about Texas, worry about the stingy Medicaid and widespread lack of health insurance.