To clarify, I think many kids are indeed let down by the system. Unfortunately the system *also* inherits problems created by parents in the first place.

IMO parents have a very important role in ensuring their children get the best out of that system as possible. Both in terms of how they raise that child in the first place, and then their subsequent involvement in their child's schooling.
I think there are too many parents (especially working class parents unfortunately) who dump their kids at the school gate, and expect to put in exactly Zero personal effort or investment in terms of supporting their child's schooling.

Parental support or indeed absence of support (or even worse), is a significant part of the equation where a child's schooling is concerned.