The studies I’ve seen on paid test prep classes is that on average they add about 30 points to the SAT, not 300. There’s a lot of conjecture here. Going to better schools and not sharing a room with siblings may improve SAT scores, but where are the studies to prove it? There are assumptions about time availability. Most businesses, including menial fast food jobs, don’t want to hire anyone under 16 to work during the school year. Even if they wanted to work, those under 16 may find it difficult to find an employer willing to hire them during the school year.