Generally speaking, "not very" and "not very", but there's no uniform standard size; you'd have to specify a particular school (and possibly even a particular bank of lockers within that school, because the school may have different sections built at different times with lockers from different manufacturers) to get an actual answer.
wise swim school in Apple Valley MN Comment: Once again even though this may be a matter of opinion this is a biased answer, you'll probably want to ask a professional instead of a 12 year old kid. I'm just saying!
The copyrighted literacy program "Wordly Wise 3000" is a spelling and grammar system used by in-school teachers and educators in the US. It seeks to develop vocabulary skills for primary, middle school, and high school students, grades K-12. (Wordly Wise is a trademark of School Specialty Inc.)
An Wise is 5' 4".
Dewayne Wise is 6'.
Seph Wise is 6'.
Anthony Wise is 5' 11".
DeWanda Wise is 5' 6".
Ernie Wise is 5' 5".
Ian Wise is 6' 0".
Marina Wise is 5' 1".
Matt Wise is 5' 11".
Roland Wise is 5' 10".