senior is fourth grade in high scholljunior is third grade, how about first,and second grade?
senior is fourth grade in high scholl
junior is third grade, how about first,and second grade?

Question

senior is fourth grade in high scholljunior is third grade, how about first,and second grade?
senior is fourth grade in high scholl
junior is third grade, how about first,and second grade?

Answer

Usually we don't call it 1st, 2nd, 3rd, and 4th grade.  It may be called the first year,second year, third year, and fourth year.

Freshman = "1st grade in high school"
Sophomore = "2nd grade in high school"
Junior = "3rd grade in high school"
Senior = "4th grade in high school"