Well remember now days in high school not all As are created equal. A B+ in certain AP classes is actually worth more than an A in the normal counter part.My son currently plays U13 MLS Next in socal. Honestly I expected better competition and play at this level. There were EA/E2 teams we played last year that are better than some of the MLS next teams this year. Three or 4 top teams including the academies are really good. The rest are average to mediocre depending on population density and what they charge players.
It takes a lot of time. Practice 3 to 4 days a week plus 1 or 2 weekend games and travel leave little time for other activities. You will travel outside the state 4 to 6 times.
We are trying it now in middle school so we can determine if it's something he wants to continue in high school. Academics is the primary focus. If MLS Next interferes with academics then we leave.
He has a clear mandate. No straight As no soccer. He has held up his end of the deal so far.
The other thing is that college admissions really is two separate tracks (three if you count the arts). One is the athletic recruited track for which (dependent on the sport for the particular college) you might get some leeway with the mean GPA but still need to meet their minimum threshold. The other is the academic for which one of the things they look at is if you are well rounded, but playing MLS Next doesn't really give you any more creed than playing AYSO...it just checks the athletic box in being well rounded. For the Ivies and some other non-tech/non-military high level privates they want you well oblonged-- to have school extracurricular, a sport, a service, some leadership, and a social life (a lot of people leaning nerdy sometimes get tripped up on this last one) but the most critical thing is being one thing you are passionate about that matches up with what you want to do in college...if you aren't going to do soccer, playing MLS Next doesn't count for that and on top of that is draining a bunch of your time.
From a purely getting into college perspective (setting aside professional aspirations, scholarship requirements to private schools, loving it, personal goals, trophy chasing, needed for military academies etc), playing something as demanding as MLS Next is a bit of a waste if you aren't trying to go the athletic recruited track. I'd say the same for all secondary level and lower club soccer except high school sports have become so competitive (as illustrated by another thread here where some high school kid went off on his school's soccer program) that to play varsity at many schools you kinda have to.