Further in my experience, the kids that have trouble with high school math are frequently hobbled because they can't manipulate basic arithmetic efficiently
In my experience, it's because high school math is taught equally terribly. No... more terribly, because the subject matter is more complex. Useless busywork and rote memorization abound.
And either way 15 minutes of homework turns into 2 hour marathons
The assignments are just awful. Doing 10 "Find the missing side of the triangle" problems does not lead to understanding. It's just an exercise in rote memorization, and so are most word problems. 99% of these problems result because our education system is simply terrible all around, and the homework assignments are abysmal too.
Whatever.