Most states give child support till the age of 18. Some go into college years.
You already signed an agreement that the child support would terminate at the age of 18 or when the school year ended.
I would not waste my money taking him back to court unless if he misses any child support payments. I would be looking at filling out FAFSA applications. Your son lives with you the majority of the time, so they would be looking at your income for this.
I hate ex's and father wanta be's that can't even take care of or help their own children. Those people have a lot of hate inside of them, and there isn't anything you can do about it sometimes.
Need to look at your state laws for college for child support, but in most states it's not a given.
((((((hugs)))))))
amy