True. If I remember Hattie correctly, he argues something akin to that reducing class sizes is mostly a political move (it's certainly not research based) — and after spending huge amounts of money on that — there is no political incentive to spend at least as much on retraining teachers.

Also, if some of the money had been spent on professional development instead of reducing class sizes in the first place, his research shows that the effect of that on student achievement had been much, much higher.