The Texas Assessment of Academic Skills (TAAS) test was the major source of data for the Texas educational accountability system from 1994 through 2002. Contrary to critics who claim that TAAS data are invalid and unreliable measures of student performance, structural equation analyses of TAAS reading data based on the 1994 Texas third grade cohort followed through eighth grade indicate that TAAS reading data meet conventional standards of trait validity and reliability. Rather than assume reading performance follows a quasi-simplex models, i.e., test scores in one year largely account for test results in the following year, an alternative conceptualization views each of the annual TAAS reading tests as one indicator of a fairly stable trait of general reading ability. A second-order factor of reading achievement provides a more reasonable fit to the data than a quasi-simplex model. Both quasi-simplex and second-order factor models indicate TAAS reading scores were highly stable from one grade to the next. (Contains 6 tables and 2 figures.)