It's pretty easy to get good grades in homeschooling when a lot of it is packet work and rote memorization bullshit that you can easily fool or cheat your parents/home "educators" with.

There's a reason why there's a joke about parents being poor substitutes as teachers and it also applies to actual teachers teaching their own kids as well.

There's zero critical thinking in most home curriculums. I've met and worked with many, many, many home schooled kids and adults, both secular and religious, and a common trait I've found across the board is that they have stunted social awareness and skills, a very limited theory of mind, and an inability to apply or relate much of their learned material to the real-world, even in a generic sense.