Here's one that makes me laugh. Locale prep school that pulls in some of the better local high school hockey players and without exception every hockey player repeated a grade there. Two kids this year moved over to the prep school and both were pretty much the bottom 20% of their respective classes. One was a gender-bender theater boy and the other plays baseball and guess what? Neither was asked to repeat a grade. Hmmm, are the hockey coaches that good at assessing a kid's academic ability or what?
If your kid was good enough to play at ISL level you would know by know. I don't say that to be mean, just realty.
Best model is...
9th grade and 10th grade at a Catholic Prep School
then - YOU will know how good your player is and you can either stay or if they are very good
Go to ISL school and repeat 10th grade.
Gives you options.
If you are making this on a hockey decision, let him be successful where he is and then "attempt" to jump to USHL or NAHL. Prep does not guarantee anything when it comes to hockey, however, he will get an amazing experience and education, that can't be disputed.