Sometimes milesplit would run blogs of athletes as they were preparing for big races like Millrose. I can't find it now, but one that stands out was Corey McGee's blog talking about how every other day she didn't have to arrive to school before 11 AM so she could go for long runs on the beach in the morning. Also, she was such a star that her tiny private school gladly accommodated her travel schedule senior year as she went to various other states to run like Texas and New York. Heck, our high school gave track kids a really hard time if you came in late one morning a year because you were attending a big meet at the NYC armory the previous evening and didn't get back home until 2 AM.
There are a number of private school kids in our state whose school coaches have no problem with them training with club teams or private coaches and running only college or even pro meets all winter and part of spring rather than lowly high school meets. In contrast, a few public school coaches would be provincial enough to have a huge problem with that. Amy Weissenbach trains with an Olympian, not the Harvard Westlake coach for example.