Using individual teacher and student-level longitudinal data from North Carolina, this research brief presents selected findings from work examining the stability of value-added model estimates of teacher effectiveness, focusing on their implication for teacher tenure policies and making high stakes personnel decisions. Findings show year-to-year correlations in teacher effects are modest, but pre-tenure estimates of teacher job performance do predict estimated post-tenure performance in both math and reading, and would therefore seem to be a reasonable metric to use as a factor in making substantive teacher selection decisions.