Contrary to the new urban myth, charter schools aren't necessarily poaching all the good teachers from traditional public schools. However, charters do appear to have some deleterious impact on the quality of the teacher force at more disadvantaged local public schools.

So says a new study looking at North Carolina teacher data from 1995-2006. It found little evidence of widespread teacher turnover at traditional public schools when a new charter moves into the neighborhood. However, the teachers who do tend to leave have quite a bit less experience than their peers.

More apparent than any problems with turnover are other kinds of impacts, such as the pressure to match higher charter school salaries or losing out on the best new hires.

The entry of a new charter school often leads to increases in teacher salaries. Struggling schools may be able to match such hikes, but usually at the expense of cutting non-instructional support services and other school programs. Also, the arrival of new charters can produce some shifts in the demographics of teachers at the traditional public schools, the implication being that they aren't able to compete as well in the market for new teachers. Disadvantaged traditional public schools are more apt to fill vacancies with teachers with only a year or two of experience--which may bring a big dose of energy, but also may lead to declining achievement.