As somebody who graduated with an IB diploma in DXB followed by a Bachelors degree from a well known university in AUS, I think it's fair to say in my experience that high-school level qualifications simply don't matter (much) here if you are a college grad.

There's nothing stopping you from including it in an "Education" section below your college qualifications though. There is no standard format, but whatever Nicksta mentioned could be used. I don't include my high school qualifications, but I do include my SAT and GMAT scores.