How do we determine whether a college certificate program is a qualified education program under the meaning of 529 saving plan?

My high school senior son is going to take a certificate program at a college while he's still studying at high school. We already set up a 529 plan for him. I remember that the 529 plan has expanded to certificate programs and some vocational training programs. How do we know if such a program would be qualified? Does the beneficiary of 529 plan have to graduate from high school before withdrawing funds from 529 plan?