senior high school

US /ˌsiː.njər ˈhaɪ skuːl/
UK /ˌsiː.njər ˈhaɪ skuːl/
"senior high school" picture
1.

a high school for students in the higher grades, typically grades 10-12 or 11-12, preparing them for higher education or vocational training

:
My brother is currently attending senior high school.
After graduating from senior high school, she plans to go to university.