There's a part time homeschool charter near us that uses this same school wide model. They do project based learning on a school wide theme, about one a month. We were definitely interested but DD was way down the lottery list, but made it into a sister school that is more GATE focused. Honestly, this is how we've homeschooled, by theme. It's worked nicely this summer with my 7yo and 3yo, and for years before DD entered school but was begging for school. I think it's a great model.