TFA says that the general problem is that

1. Parents are now the primary enforcement mechanism for doing schoolwork, which is not a role they have necessarily been trained to do

2. Teachers do not coordinate the amount of schoolwork, so parents are in the unenviable position of essentially executing multiple lesson plans in place of the multiple teachers, each which is probably complex in its own right.

2 was a problem when I went to public school normally and 8 teachers each giving 45mins-1 hr of homework easily added up and ate into free time. Now parents are actually exposed to the problem.