Is this in Oregon?
Different laws apply to different states with respect to child support and college.
In Oregon, a court may provide for the support of a “child attending school” anytime during or after a divorce. To qualify, the child must be 18-21 years of age, unmarried, enrolled at least half-time at a school, community college, college, university, or regularly attending professional vocational or technical training, and must be making satisfactory progress as defined by the school.
Additionally, once a child qualifies as a “child attending school”, child support must be paid directly to the child unless the court orders the money to be distributed otherwise. The child may use the child support at his or her discretion. This means that the child is not required to use the money to pay for tuition, books and supplies, but rather can use the money however he or she best judges that it should be spent.
Not every state does it like this, so if your child were enrolled in school at least half time by August and progressing through school (i.e., he continues to maintain his grades), Oregon says that the money should be paid directly to your son in that instance. My apologies for the incorrect information earlier.
Now, as to paying for college, does your order actually say that you have to pay for college? Unless one or both of you are ordered in the court order to do so, neither one of you has an obligation to contribute to the costs. Could your ex petition the court and ask that you pay? Yes, but generally, it is very rare that a court would make a parent pay for college tution or other costs -it would have to be a situation where for example a child may have to drop out because they otherwise cannot afford to go, and a parent has the financial means to pay.