Papay and Kraft also found that teachers vary a lot in how much they improve over time, and that teachers in some schools improved more, implying that school conditions play a role in promoting or
constraining teacher growth.
The NFER has also said that «the lack of
growth in curriculum time could be due to reduced
teacher supply
constraining schools from expanding provision in these subjects», but that «school and pupil preferences may also be influencing these trends».