You could call them 'high school students' or even 'high schoolers'. That would suggest the students are in grades 9-12 (depending on the.
Twelfth grade, senior year, or grade 12 is the final year of secondary school in most of North In many Canadian high schools, students during their year, hold a series of fundraisers, grade-class trips, and other social events. Grade 12.
A high school offering the last years of secondary education, usually consisting of grades 10, 11, and 12 - Senior high school is a secondary school that students.