Any time a player hits a 2.5 gpa (and sometimes even a 2.6 given all that player's factors) I almost always increase the study hall minutes by half...so if they were set to 4 minutes then I would move them to 6 minutes. This is because those gpa's aren't a direct reflection of what those amounts of minutes produce in that player. Which is why a player with a midterm of 2.5 could end-up failing that term...because at that moment they were in the middle of their landslide rather than settling at the bottom.
Just had a guy after the first midterms with a 1.9, he'd initially been set at 5 minutes so I moved him to 10, but got a little paranoid with three or so days before term grades came out and bumped him to 12 minutes...he ended-up with a 2.1 gpa. Any time a player hits 2.0 or below then I set them to a minimum of 10, but given this guy was a redshirt (with okay WE but low high school gpa) I upped that and now I feel like I'm extremely lucky that I did.