A recent case by an appellate court makes clear that a parent may deduct college expenses paid for room and board from his child support obligation pursuant to a court order. This result can be avoided by a carefully crafted separation agreement that contains a provision that no such deductions will be allowed.
Remember once an agreement between spouses is reached and reduced to writing it will be governed by contract law that will not permit modification, unless agreed to by both parties. If you receive residential custody, such a clause would be of great benefit and allow you to continue to recieve the agreed upon amount of support even while the child is away at college. It may save thousands of dollars in support.
Your attorney should be familiar with the holding in Ataande v. Attande that discusses these principles. At this writing there is no legal citation, but when the case appears in print it will be easily found by name.