You're where I was at a few years ago.
My solution was to have my own version of summer school, covering subjects 'taught' over the last year as well as touching on things for the next year.
We stick to basics. Math, geography, history, English, etc. Things that have been sacrificed in the schoolroom for entertainment and indoctrination.
Most schools have their curriculums online, so you know what will be covered.
You can also request any and all materials from the school so you can examine them.
I've opted my girls out of numerous 'do-nothing' activities, and requested that the school give them alternate academic assignments.
If you think science is bad look at history textbooks. To say that they lie would be an understatement.
Above all, I've taught my girls that
1) A teachers word is not gospel, but you have to put what the teacher wants on the test
2) Printed material should be taken with a grain of salt unless corroborated by another source.
3) If they ever have any questions about what they've heard in school, let me know and we'll research for the truth together.
It's worked out pretty well. They get A's and B's in school and many teachers have told me in private that they are much more mature than most of their contemporaries.