I saw it this way,
No student should get all three prizes so a student can get one or two prizes.
For distributing 1 prize for 3 each students
select 3 students out of 5(5c3) and then 3! ways to arrange/different ways to distribute among those three students.=>5c3*3!
For distributing 2 prizes cases we would have to select only two students so that one student gets 2 prizes and the other student gets 1 prize.
Select 2 students from 5(5c2) and then for the guy who gets 2 prizes we can select 2 prizes out of 3 prizes in 3c2 ways. Now in those two students we can select a guy further for 2 prizes and the other guy gets the remaining prize .we can do it in 2 ways.=>5c2*3c2*2
So add both cases 5c3*3!+5c2*3c2*2
=5c3(3!+3*2)
=5c3(12)
=120.