If you have a Parenting Plan in place, it should indicate if the issue of post-secondary education and support was agreed to, waived, or left open. Generally, if the issue was left open, the person requesting the support needs to file for modification before the child turns 18 or finishes high school, whichever is later.
An agreement can be made as to how long and what amount of support needs to be paid. Otherwise, the Judge will make the final decision. An attorney can help you decide what your best course of action is.