If a school is split, having both middle and high school, those in 6th through 8th grade are in Junior High and those in 9th through 12th are in high school.Generally, high school starts at the 9th...
generally, it's 9th, though I think a few sometimes start at 8th. 8th is already pretty uncommon, so there's about one millionth of a chance you'll/you have/you should have gone to a high school...