Not much is publically known about it. This, from 2015 sounds good:
Musk hired one of the teachers from the boys' school to help found Ad Astra, and the school now teaches 14 elementary-school-aged kids from mostly SpaceX employees' families. The CEO wanted his school to teach according to students' individual aptitudes, so he did away with the grade structure entirely. Most importantly, he says learning should be about problem solving."It's important to teach problem solving, or teach to the problem and not the tools," Musk said. "Let's say you're trying to teach people about how engines work. A more traditional approach would be saying, 'We're going to teach all about screwdrivers and wrenches.' This is a very difficult way to do it. A much better way would be, like, 'Here's the engine. Now let's take it apart. How are we gonna take it apart? Oh you need a screwdriver!'"
"Some people love English or languages. Some people love math. Some people love music. Different abilities, different times," he says. "It makes more sense to cater the education to match their aptitudes and abilities."
But unlike other schools, it doesn’t teach music and sports and language arts appear to be an afterthought, according to Ars. The reason? Musk thinks it’s more important for children to learn other topics when computers can take up the task of translating language in the future.
The school is called Ad Astra, "to the stars".