How much does Catherine need until she hits the goal? At least 4000 but probably more since she’ll want to get the hell out of there.
Also, if all the kids graduated the Wagners early, which of them actually have an education? Besides the creationism and whatnot, was Sophia as rigorous as she should have been?
Since Catherine's discontent with her family/current lifestyle is more of a story thread than anything else, and due to the fact that I use a very weird mishmash of "real" and "Sims" elements*, I don't have a specific number in mind.
Re: education, Sophia's teaching and the curriculum(s) they use (including the official ISCS one) doesn't make for the best education in the world, but they aren't scraping the bottom of barrel either. Everyone knows the basics. (In fact, Sophia knows more than "the basics"--she has a BA!) Plus SLC's ongoing presence has made it harder for the Wagners to commit serious educational neglect. And the gimmicks they do for filming (field trips, vacations, et cetera) are the cherry on top in terms of extra educational content they wouldn't ordinarily get.
The Wagner kids also have access to books because--while I wouldn't call the ISCS community especially intellectual--reading is seen as a decent, family-friendly pastime. It's certainly preferable to other, more sinful activities. I imagine the books in the Wagner household are a mix of modern and older Christian materials (fiction and nonfiction), history content that conforms to their worldview, and then the classics, because they're "clean" and "support traditional values." For a kid like Catherine, who is a huge bookworm and highly motivated to learn about the world outside the ISCS bubble, access to the classics is an amazing resource for her: they're both genuinely educational and not likely to get her in trouble. Most of the kids have read a few classic novels for a homeschool project or for fun, so they aren't completely screwed, educationally-speaking. Just not quite as driven as Catherine is. (And for that discrepancy, I don't have a particular justification; it just happens in families sometimes, even when children are raised exactly the same. But that's a conversation for another post lol.)
*(i.e. I typically choose the English text option in CC items, and I use a real-world timeline for aging. However, I also use the game's names for worlds/"towns.")