Does eliminating tenure makes any difference in the quality of the teacher workforce (as judged by achievement test score gains)? The Brookings Institute published an article that sheds some light on the impact prior to 2011. By comparing the departure rate of teachers with lower gain scores to those with higher gain scores, one would expect more lower rated teachers to leave.
Not so, say the authors of the study. Among the top new teachers in terms of value added achievement gain scores (in North Carolina), only 54% were employed anywhere in the state five years later. The lowest quarter remained in the state at about the same rate (50%).
Results for Florida’s new fourth and fifth grade teachers were similar. These teachers were tracked over five years (2000-2005). Teacher mobility was high and primarily voluntary. Ten percent of new teachers left the state after one year, and by five years, 27% of those new teachers had left. The teachers were equally likely to have had lower or higher effectiveness ratings. Newly hired teacher attrition actually declined during the recent recession, probably because there were fewer alternatives. The patterns of retention, however, remained the same.
Teachers who switch schools tended to move to those with more advantaged student bodies. Effective teachers, however, were no more likely to leave low performing schools than were ineffective teachers. Principals with more advantaged students were able over time to weed out more teachers with lower gain scores. Thus, less effective teachers may be rotating among schools. This may be due in part to market factors, the researchers suggested. The pool of teachers may not be sufficiently large to replace all ineffective teachers.
Is it even possible to reliably identify highly effective or ineffective teachers? A Vanderbilt study of four large Florida counties during the same 2000-2005 period indicated that only 20% of teachers with the highest gain scores earned top quintile scores the following year. The teachers’ effectiveness scores changed due to the variability in the learning rates of individual students as well as the assignment of teachers to different classes.
Many teachers scoring in the lowest quintile also shifted substantially in their ratings. Which students were in a class and to which class a teacher was assigned had the most impact on a teacher’s gain scores. Even averaging gains across multiple years did little to improve the stability of teacher gain scores for elementary grades.
It may be telling that gain scores for middle school teachers were more stable. Since middle school teachers are divided into subject areas and students may be grouped by their level of achievement, the students’ scores in a class are likely to be more similar than in elementary schools.
For most teachers, gain scores are fairly random from one year to the next. For these reasons, the Florida legislature reduced the percentage allocated for gain scores from 50 to 30% in the formula used to determine teacher effectiveness.
The take away? No doubt that changes in teacher evaluation and dismissal policies make it easier to dismiss the most egregious cases. It also discourages teachers who must comply with the state requirement for 300 hours of ESOL coursework. In Alachua County, eighty teachers and/or principals (~5%) faced non-renewal of their contracts this year.
The continuing chorus about the poor quality of the teacher workforce, however, does little to improve the retention of the most effective teachers. Florida’s attrition rate is eight percent which is higher than the national average and higher than California, Texas, and New York according to a University of Pennsylvania study. Attrition at low income schools is fifty percent higher than at higher income area schools. The differences between teachers in struggling and affluent schools is one of experience, not quality.
Teachers vote with their feet. To avoid looming teacher shortages, the public must vote to support effective teachers.