I was 5'8" entering High School. I graduated 6'7".
Son #1 was 5'8" entering H.S., graduated 6'5".
Son # 2 entered H.S. this year at 5'8". Finished freshman year at 6'1.5". My best guess, he'll end around 6'8" - 6'11".
It doesn't take a genius to look at a kid and figure out whether he's still got room to grow or he's close to done.