MANY US school leaders believe that the nation's worst-ever staffing crisis is now inevitable.
About 200,000 teachers will have to be recruited annually over the next decade to compensate for rising student enrolments and a sharp increase in teacher retirements.
Some analysts doubt whether that is possible, especially as states such as Massachusetts have had to introduce "signing-on bonuses".
But Richard Ingersoll, of the University of Georgia, believes that states should be thinking about teacher retention as well as supply.
"There is no point in recruiting hundreds of thousands of teachers if they leave a few years later," he told the AERA conference. "What the data suggest is that we have a revolving door."
Ingersoll's research shows that teacher turnover is running at 13.2 per cent a year - compared with 11 per cent for the general economy. Predictably, public scools in poor urban districts have a higher turnover (15.2 per cent) than those in better-off areas (10.5 per cent).
But his research - based on US Department Education statistics - also produced a surprise. Private schools' turnover (18.9 per cent) was far higher than public schools' (12.4 per cent).
Small private schools had the highest rate of all (22.8 per cent).
In small private schools, inadequate pay was the main source of unhappiness (76 per cent of dissatisfied leavers mentioned salary). But teachers in disadvantaged public schools were unhappy about various issues: salary (31 per cent), administrative support (23 per cent), student discipline (28 per cent) and unsafe environments (15 per cent).
However, Ingersoll does not believe that his statistics are depressing. "If we want to improve retention rates we need to look at the way schools are managed and run. But they are not problems beyond our reach."