"Stay out of sight," you advise Briar in a low voice.
"Duh," she retorts, before tucking herself as far down in your pocket as she can go. Even her glow dims, to the point where it doesn't penetrate the light fabric of your shirt. "Dial down the aura, kiddo, and stay as far away from that creep as you can. I'll do what I can to help you hide, but if he's some kind of sensor..."
Briar doesn't need to finish that sentence. Taking her advice, you call on your spiritual training and suppress as much of your magical energy as you can. It's not exactly easy, less so for being something you've never really attempted before, and the results are less than perfect - you'd probably register as a strong, untapped talent if you were directly scanned like this. Then you dimly sense Briar doing... something. You're not sure what, but it causes your aura to diminish further, to a level akin to a weak untapped talent. That feels like it's about as good as you can hope for, under the circumstances.
Gained Spiritual Prowess E+
Quietly telling Moblin to stay at the back of the room, you sidle over to Amy and advise her of the situation. She looks horrified, and starts restraining her aura before you even suggest doing so. She doesn't have as much natural power as you do, and her control is pretty good, so she ends up disappearing from your senses altogether. Cordelia and Larry don't have the training to do anything about their auras, but on the other hand, what magical potential they have is fairly minor and entirely undeveloped. You know from Briar's little spree of "testing" that nobody else in the class is any stronger.
This is probably as good as it gets.
Your teacher instructs everyone to take a seat and get out an eraser - special pencils will be provided for the test. You and Amy pick a table about halfway back from the front, over by the windows, and Larry, Cordelia, and Aura join you momentarily. The demon, meanwhile, has settled in at the teacher's table, silently counted heads, and produced the appropriate number of test papers from his briefcase. You breathe a silent sigh of relief when your teacher hands these out. As you take your test, you can just dimly perceive a spell of some kind linking the paper and the pencil. The one on the paper is entirely passive towards you, but as soon as you touch the pencil, you feel it pulling at your aura. The sensation is feather-light, a whisper that you doubt you'd even notice if your magical training were any less advanced than it already is, and it doesn't feel hostile or coercive, just curious.
A two-part analysis spell, then. The pencil samples your aura and channels a bit of it into the paper, which preserves it for later, more detailed testing. You have to admit that it is a subtle and efficient method of weeding out potential magic-users on a large scale; you wouldn't even need a particularly skilled caster to create these tests or measure their results. Your inner tyrant approves of the practice in theory, but by the same token, you really don't like the idea of some demonic bureaucracy having a copy of your magical signature. There isn't much you can do about it now, though, unless you're willing to take a chance and enchant your test for later tracking and retrieval or destruction.
You glance at the demon. He's talking quietly with your teacher, occasionally peering at this or that student. You've not sensed any active use of magic from him since he entered, it's all been pre-enchanted items. The aura of dark magic you picked up before could have just been his essential nature, not a sign of actual mystical ability. Or he could just be really good at concealing his spellcraft. One point against him is the fact that he doesn't appear to have noticed Moblin.
Do you want to cast the tracking spell?