Unlike most subjects, science is difficult and there's usually one specific answer. It's near impossible for the amateur to stumble onto something new - odds are, somebody has already had that idea and it didn't pan out.

When I taught math, the answer to a five point problem was worth zero. Students would protest, but what good is the answer if you fumbled the steps to get there? So I graded the steps.

Other students would complain (and I've heard comments recently) about how "I didn't like math because I didn't want to do it the teacher's way, and they hated that. Forget the stupid 'rules,' I do it THIS way." Or, "I don't write it down, I just do it in my head. Don't I deserve credit?"

No.

Because what you've uncovered is either accidentally correct or based on a faulty solution that didn't happen to interfere with this particular problem. You're welcome to do the problem a different way, but I need to see your work - every step of it - so I know if you're performing logical operations. If so, cool, full points. But every problem has a number of simple, elegant, and obviously correct solutions...that turn out to be bunk under close examination.

Hard to B.S. the science exam.