I had something similar in elementary school. There was an assignment given and something like 2 hours to do it. The reward was extra recess time. I saw the exercise knew I could do it quickly so I screwed around for about 1 hour and 50 minutes. The teacher saw this and commented on it. In the last 10 minutes I blasted out the assignment, handing it in when everyone else did. I received a passing grade on the assignment. The teacher stopped me anyway from getting the extra recess time because she didn’t like that I spent so little time on the assignment even though I completed it sufficiently.

I stopped trusting teachers for years because of that and so no reason to put in full effort when arbitrarily applied rules would take away the rewards anyway. That didn’t mean I didn’t put effort into learning, it just didn’t really care about scoring well or doing assignments. I’d do well on tests, but had low grades from simply not completing or not turning in homework. Occasionally I’d even do the homework if I was working on grasping the concept being taught, but I didn’t see a point of even turning those in many times even though they were complete.