In fact, the only two observable factors that have been found consistently to lead to higher student achievement are class size and teacher experience, so that it's ironic that these same individuals are trying to undermine both.
Generally speaking the corporate reformers argue that only the first few years of experience matter, though you can see from these charts from a study by Thomas J. Kane [now at the Gates foundation] Jonah E. Rockoff [DOE consultant] and Douglas O. Staiger reveal that at year five, effectiveness is still going up for all categories other than uncertified teachers. (see charts to the right.)
Of course, most Teach for America recruits are gone by then, which is why their dotted line vanishes at year three.
Actually, there are many studies that show that teaching experience matters, for 15-20 years – with each year in the profession leading to more student gains, especially in reading.
In fact, the importance of experience may be clearer in the teaching profession than any other, as shown in a recent re-analysis of the STAR Tennessee experiment, showing that Kindergarten students had higher achievement and earnings as adults, depending on how long their teachers had been in the profession, with gains for every year up to twenty.
Another study of low-performing, high poverty schools, shows that years of teaching experience at the 2nd grade level was associated with higher reading achievement, for up to 20 years.
“A teacher who had been teaching at a particular grade level for more than 5 years was positively and significantly associated with increased student achievement (effect size=.27)…grade level experience was sizable compared to race (minority status effect size = -.33) and SES (economically disadvantaged effect size= -.08)….Teachers constantly improved teaching effectiveness until the 21st year and declined beyond that.”
See also this study of Florida, showing that for 4th and 5th grade teachers, "in elementary school reading there may be student achievement returns to as many as 15 years of additional teacher experience."
Actually their graph (to the right) shows gains in reading for up to 30 years!
So when people who claim to care about kids advocate for laying off experienced teachers, don't believe them.
Private schools and well-funded public schools don't have to choose between having experienced teachers and smaller classes, and neither should our public schools.