Why didn't Greg ever send Steven to school?

I was rewatching "Mirror Gem" a few weeks ago, and I was struck by how unfamiliar with school Steven is. He doesn't even know the basic concept. At the time of season 1, we just assumed it was because he was living with the Gems for most of his life, plus his age was more ambiguous back then. We now know he was 13, but he could've been 8-10 for all everyone knew. However, the "We Are The Crystal Gems" music video shows Steven moving into the completed Gem house/temple around the same age he was at season 1. This fits because otherwise it would be weird for him to live with them for years without knowing what fusion and other stuff is etc...

but it begs the question....why didn't Greg ever send Steven to school before then? How could Steven have lived with Greg for 12/13 years and have no idea what school is? Especially after being around other kids like Peedee.

Greg is totally best-tv-dad-ever, but not sending Steven to school bothers me a lot.