Jeremy is behind on mana. 

He's not very far behind, not yet, but whenever he has to choose between homework and sleep and learning spells from the void, he finds himself putting off mana-building. He has a backup plan for mana, and there's no way to make a backup plan for dying because he's too tired to spot a mal.

But now it's midterms time.

Most of his midterms aren't very difficult, or at least aren't difficult enough that he's at actual risk of failing ("In at least 1000 words, analyze the role of death by violence in a work of your choice from this course.") He's a little worried about his Modern Magical History essay, which Briar is writing for him by preexisting arrangement, but even Briar can't possibly mess it up badly enough to fail it outright.

The trickier project -- the reason that he's kneeling on the floor of his room, staring at a mouse tank that he's pulled out from under his bed -- is his shop assignment. They've finished covering the basics of the materials they'll be working with, and they're starting to be assigned more advanced projects, some of which go beyond techniques for working with physical materials into actually incorporating spells into the artifice -- nothing especially complicated, but enough to learn the basics of how to do it.

Objectively speaking, his shop project isn't difficult. All he has to do is create a belt out of interlocking wire loops, which isn't actually difficult compared to most of the techniques they've learned. The problem is that he also has to individually enchant each loop with a spell designed to reinforce it, included with the assignment sheet. Casting the spell once wouldn't be a big deal, but casting it enough times for the entire belt would be enough to wipe out most of his mana-building progress since arrival. 

Jeremy doesn't, really, need to build mana for graduation. But he can't rely on pulling malia from the mice in his room if he gets ambushed on the stairs between classes, and it's not like he can just carry a mouse around in his pocket for emergencies.

Pulling malia here is risky. One time isn't enough to acquire an aura, but it makes subsequent malia use more dangerous, both in terms of the aura and in terms of being able to keep using regular mana. Even putting aside the actual effects of pulling malia, if you have some sort of shortcut around a problem, Jeremy is fully aware how easy it is to just start using that shortcut every time, even when you don't have to. 

Dipping into his mana supply is risky. If he ends up fighting something particularly dangerous in the hallways, he won't be able to pull from his mice, and even if he's just attacked at night he might not be able to grab one in time. It's almost Field Day, and everyone knows that the school gets deadlier after Field Day.

(Inside its tank, his mouse squeaks.)

Fundamentally, Jeremy thinks, this is a question of timescales. In the short term, it's definitely safer to just take the easy route of using malia, but if he makes that decision every time, he'll be dead well before he ever reaches graduation. He works through a few estimates of how much mana he'll have left over -- probably enough that he'll be able to fend off anything that wouldn't be strong enough to kill him either way, he thinks, although that's not accounting for the possibility of repeat attacks -- but those are much more likely to come from common, weaker mals --

--What he really needs is some way to carry his mice around with him. After midterms he can try to research that. For now, he needs to focus on finishing this project; delaying it isn't going to make it any easier.

Jeremy slowly slides the mouse tank back under his bed.