And they are entitled to make decisions themselves.
True. But it’s the parent’s money.
Yes, and the parents are entitled to make their own decisions with their money. So they can tell the kid they will only pay for certain yeshivos or colleges.
There was a guy in Israel once who has a son who had gone OTD. This son asked him for a car. The father apparently could afford the car, but told the son he would buy it only if the son promised to not drive that car on shabbos. The son said no deal.
The father consulted with Rav Shach. Rav Shach told him to the buy the car- no strings attached. If you still have a relationship, you can hopefully still influence your kid for good.
Try telling your kid you will only pay for certain yeshivos. See what it does for your relationship.