It really really really depends on the barn that the horse is going to - Here is my experience with IHSA and IDA horses:
I used to manage an IHSA/IDA barn - the horses can have a tough life. Ours did lessons 5 days a week during the school year, sometimes 2 rides per day. They then did lessons and summer camps during the summer for local children. That made them fit enough to be used in the IHSA shows where they may jump 5, 10, even 15 rounds a day. Our region had each school host 3 shows per weekend, so two full shows sat and one sun - that meant our horses did 30+ rounds (flat and jumping) on sat and 15 or so on sun. At a show, the coach doesn't have the ability to choose which riders ride which horse (unless it's IDA where there are "groups" of horses and the coach does try to find the most suitable combos) so a horse may be subjected to a much rougher rider than is neccessary. Quite a few nice h/j'ers who had been successful on the show circuit were too sensitive to have so many different riders on them and they were given away or sold.
Beyond the workload, most programs have a very tight budget. I was allowed $1,000 per horse per year for feed (hay and grain), farrier, and routine vet. There was very little for emergencies and I often paid out of pocket for first aid items. My coach was a fan of having nice horses donated, then turning around and selling them out of area for a huge profit. He said that the proceeds went to buying hay and supplies - but being "in the know" I was handling a lot of the expenses and know that wasn't really happening.
On the plus side, our horses were turned out 24/7 and in a herd, so they had good "horse lives" they all were handled every day and shod regularly. We adressed any lameness right away because taking care of a small problem was far better financially than waiting and having it turn into a bad one. Although any major issue usually resulted in re-homing or euthanasia (one time I was on the phone with someone to take a horse that was just starting to founder - the person had the resources to take care of the horse and rehab - but by the time I walked out from the office at the vet to the work area, they had already put the horse down, despite knowing what I was trying to do). They do have a rider every now and then that dotes on them and brings treats and grooms them for hours and hours.
So I guess what I should be saying is this - Do a care lease and make it clear that if the college doesn't want to continue to care for your horse or use your horse, you get it back. Set a limit to the number of rides per week, level of rider, and height of fences. Make sure you have a way to check in on the horse while it is at the college. Visit their barn ahead of time to see it and the condition of the horses - without an appointment.
If you want to know which school I was at PM me - I'll tell. It was out west.