Is it better for cheaters to get caught in the future or immediately?

I just got out of my psychology class where we were taking a test, and these two girls beside me were definitely going over their answers (I think it’s b, no, its definitely a, etc). I told the teacher discreetly (writing it on the back of my test and showing it to him when I turned it in), but I just don’t know if I really did the right thing.

I know that cheating is wrong, and I know that its because you’re not being honest with work and things like that, but is it better to let them get caught in the future or to tell on them immediately?

I already told him, so there’s no way I can get that back or anything… but which is it?

I love how the answer was definitely not a, but it was d…