I teach many students. Therefore I want to say that I made written tests and gave test scores and graded those students attitude also. Should I write student's to mean I graded each student or students' to mean I graded all of my students?



Write '... and graded those students' attitudes also'.


I graded a student's paper.
I graded all of my students' papers.

However, you can also use the noun 'student' as a modifier:

I graded student papers all day yesterday.