The intent of the No Child Left Behind (NCLB) Act of 2001 is to hold schools accountable for ensuring that all their students achieve mastery in reading and math, with a particular focus on groups that have traditionally been left behind. Under NCLB, states submit accountability plans to the U.S. Department of Education detailing the rules and policies to be used in tracking the adequate yearly progress (AYP) of schools toward these goals. This report examines Texas's NCLB accountability system, particularly how its various rules, criteria and practices result in schools either making AYP, or not making AYP. It also gauges how tough Texas's system is compared with other states. Looking across the 28 state accountability systems examined in this study, Texas is among the least restrictive in terms of how many sample schools make AYP. Texas proficiency standards are relatively easy, and Texas has a relatively large minimum size for subgroup reporting, meaning that schools in Texas will have fewer accountable subgroups than would similar schools in other states. Unlike most other states, Texas does not report a confidence interval around its proficiency rates. Compared to the other 27 states examined, Texas places in the high end of the distribution in terms of the number of schools making AYP. The report concludes that although in some respects, Texas's NCLB accountability system is working as intended by the legislation, NCLB shortcomings are also evident, and should be considerations for Congress in future reauthorizations of the act. (Contains 8 footnotes, 3 figures, and 4 tables.) [For "The Accountability Illusion," see ED504712. For individual state reports, see ED504680-ED504694, ED504700-ED504711 and ED504719.]