It has been asserted that the test-based accountability of No Child Left Behind (NCLB) increased instruction in tested subject areas reading and math, leading to reductions in arts education. We tested this using two waves of data, before and after NCLB implementation, in a difference-in-differences design. The analyses indicated that the total teacher workforce increased substantially during this time period, while the percentage of reading and math educators remained constant, leading to an overall increase in the teacher corps for these subjects. In contrast, the percentage of music and visual arts educators decreased during this period, leading to a decrease in their numbers. Average subject-specific teaching loads increased across all of these subjects. The result was substantial increases in the number of reading and math courses taught, combined with overall stability in the number of arts courses. However, comparisons across states with varying implementation of test-based school accountability prior to NCLB failed to show a relationship between such accountability and changes in the percentages and teaching loads of reading, math, and arts educators. Thus, at least in terms of cross-state comparisons, changes in these outcomes cannot be attributed to state-specific changes in accountability brought on by the introduction of NCLB.