TOEFL essay question (high schools should allow students to study the courses...)

[Cannabis Sativa]

hi, i've got quick question on writing toefl essay
let's say you have Agree or Disagree type essay; for instance, "high schools should allow students to study the courses that students want to study"; is it mandatory to stick to one opinion??
Can i say that it depends on a situation and compare two situations, when student knows what he wants to do in future(as far as profession) and chooses courses accordingly; and another situation, when student is not sure what to do in future, and say that he will benefit more if high school will tell him what courses to take??
will i receive a lower score for not sticking to one opinion??