States use licensing to ensure that only qualified teachers can be hired, but loopholes often allow teachers to enter the classroom via alternate routes. Comparing the performance of students whose teachers hold standard certificates with students whose teachers have non-standard credentials is one way to gauge the efficacy of licensing. Using data from the National Educational Longitudinal Study of 1988, this study finds that students whose teachers possess a B.A. or M.A. in math outperform other students in math. Students whose teachers have any kind of certification (standard, emergency, alternative, etc.) outperform students whose teachers have no certification or are certified in a different subject. The authors also report that math and science students whose teachers have emergency credentials do no worse than those whose teachers hold standard teaching credentials.