The purpose of this study was to investigate whether the Watson-Glaser Critical Thinking Appraisal-Form S was a reliable and valid instrument to measure critical thinking for students pursuing a teacher career. The participants were 137 students enrolled in Educational Psychology. The data showed that the alpha for the total WGTA-FS was 0.76 and the split-half correlation was r=0.44. The total WGCTA-FS score correlated significantly with course grades r=0.32, p less than 0.01. Since the range of the course grades was large, further analyses were done to determine the differences between high-grade and low-grade achievers on the WGCTA-FS. (Contains 3 tables.)