Yes, child support can continue after the age of 18 for a number of reasons (although it will depend on the circumstances). In fact, child support can continue into the university or college years, for example where the now-adult child is working towards getting a degree – and in some rare cases, even two degrees.
Under Ontario law, the test is not that the child is “full time in high school”; rather, he or she must be “enrolled in a full-time program of education”. If your child qualifies, you and the other parent may be obliged to cover some or all of his or her tuition, living expenses, and even special or one-time expenses that relate to the program.
In your case, if the child is over 18 but is still enrolled in a full-time program and accumulating university credits, this will likely meet the test. However, you should obtain the tailored advice of a Family Lawyer who can review your situation in greater detail.