I think the biggest problem of math education is that it’s not taught in a way that maximizes long-term memory. There’s a lot of research on it but I think there’s lots of methodology in teaching on how to make students remember better that’s underutilized. An example: interleaving old problems in tests and homework. Doesn’t take much work but from what I remember there are studies that show significant improvement in final tests scores and likely in overall recall. Depending on students to review older material on their own isn’t a good bet.