I can only comment on what I saw as the parent of a CC player. It did happen, but not quite as often as many believe. It was more common for a kid to play at the CC school for 1 or 2 seasons, and then see him re-class when he moved to prep in his sophomore or junior years. Most of the kids who entered in 7th/9th grade with my son were in the same birth/hockey year. We saw a few players peel off to prep schools over the years (and some went back to their local high schools), but the rest graduated with him. The players who stayed at the CC school and wanted to play hockey in college, typically went the PG or juniors routes to make up the age difference. Most of those kids are now playing at D2/D3 schools.
That is why it is a waste to reclass early and repeat as a freshman or sophomore. Let it play out and see the development. Kid is usually a different player at 17 than 14.
My son did it a little different and repeated as a Junior due to the opportunity, turned out great for him. Played 2 years at Prep and USHL as 20 year old D1 next year. He was very lucky to get this opportunity