Frustrated at Lackluster Public School, Need Advice

Met with my kids AP teacher during parent weekend. Teacher said usually the whole class gets 5’s on the test with a couple of kids scoring 4’s. Expectation was a 5.
That’s why I don’t mind paying for BS. The expectations are higher and the kids are prepared for any college.
Kids from mediocre schools can catch up and Ivies know that but they also know that some don’t. There are programs in place at Ivys to keep some from dropping out. Many switch to easier fields. Was like this whenI was an Ivy student years ago. Now even more programs. People know who is not keeping up and so do the teachers. That doesn’t mean every Ivy acceptance results in success. Many transfer, some take the easy classes, some buckle down and do the hard work.
Poor preparation in hs will definitely be felt down the road. Even if the intentions were good, exposure to expository and research takes time to learn. Most lackng skills I saw were writing, ability to speak well in class and math/science issues.
The schools aren’t perfect at acceptance either. There are kids at Ivies who will be at the bottom of their class just like any other school. It’s not a matter of intelligence but an issue of time. Kids may not have enough time to catch up and still do their work.