Matt Wiswall has a nice Bill Gates’ quote about teacher experience.
Once somebody has taught for three years their teaching quality does not change thereafter.
That quote is a pretty fair representation of what past research has shown. Well, maybe gains continue for five years, but not more than that. (We’re talking averages, of course. Some teachers do continue to get better for many years and some burnout.) Wiswall gives us a picture of what other researchers have found.
You can see that three studies show no gains after three to five years. Two studies do show gains continuing for a while longer, but then flattening out.
Wiswall took data on essentially every fifth grade public school teacher in North Carolina and estimated a very flexible relation between student outcomes and experience. Here’s Wiswall’s picture from his own research.
What’s different is that Wiswall’s estimates suggest that teachers do, on average, keep getting better throughout their career.
Very different from the received wisdom. More recent evidence on teacher experience next time.