Probably??
When writing the bio-- wonder why the heck I'm still in school
at that age Possible ideas is that the school branches off into
University/Colleges? But then theres the Year 1 to 4 option.
Thinking from a high school perspective- year 1 is obviously the
freshmen. So age wise should be 15 maybe. 2nd year- 16, 3rd- 17
and 4th year would be 18. Make sense.
21+ make me think... special case. Maybe our character came
into our powers late and had to be admitted into the school at such
an odd age.
Thats how I made my bio anyway... my character didn't realize she
had magic until she was 20. lol