I like what's going on here. I think there are some great bits of voice. The "already-getting-on-my-nerves freshman" made me smile, and the introduction of the brothers is great. I love that the MC is apparently quite comfortable with picking locks.

I do believe there is more you could do with this voice. The MC is snarky, intelligent, and I'd love that to shine through more. To me, the prose feels a little forced at times, and I wonder if you need to start with the explanation. Why not start with the lockpicking and filter it in, for example?

I'd love this to be a bit snappier, but I do think you're off to a good start.

Really great first sentence and voice in the first paragraph!

This might be an instance where I’m finding the voice a little too strong. The second paragraph is confusing to me – the phrases he uses, with all the hyphens, aren’t placed in a strong enough context (yet!) for me to know what they mean. So even though this might be the language he uses to think about these things, I don’t know him well enough yet to understand them. Move them to later on, or use some more accessible terminology until we become better acquainted with his voice.

Again, here’s another instance of nice dispersion of one-word thoughts with full sentences – reminds us that we are in a character’s head, and lets us think along with him.

The voice here is strong, and I do feel like I know this character well enough. But I think that, because of that second paragraph, it might be a case of the voice being brought in too strongly, before we can grab onto it.

Great work!

Wonderful voice here.

I do have some suggestions. Like, maybe you could change that first 'normally' to 'usually' so we don't have too many 'normally's right off.

The third paragraph confused me. You might want to rework it to make it clearer. How do these circumstances make it special? Do you mean that all three things combined made it a perfect scenario? If he wouldn't normally risk it, how are these things unique to make him take the risk? And what is his motive now. Had he not had a motive before? Are these secrets you want to keep for later? You could clear this up by adding a few more details to this paragraph. Sort of like this...

'But how could I resist? I had motive--a failing grade, thank you very much Mr. Taylor. The means to getting to the test, thanks to Gil and Lew. And I had a perfect alibi, courtesy of hooking up with a pretty, but already-getting-on-my-nerves fifteen year-old freshman, two weeks earlier.'

This sample is not that great but gives you an idea of what I mean. Of course this probably doesn't fit your story, and you should put it in your voice. Plus it could just be me and others may feel differently.

Other than that, I really love this, and I'm interested in the science fiction aspect of the story.

I think the voice here is already strong. I have a clear idea of who the MC is, his POV and how he interacts with his world. I think it's just a matter of clarification in certain areas to tighten everything up.

IN-LINE CRITS
When Gil and Lew came to my dorm room with the idea of stealing the physics final, I normally wouldn’t have considered such a dumbass move. (Nice. This right away orients me to the MC's tone.) Not that I had any moral objections to cheating or stealing. But normally, the potential for a high grade on a single test weighed against getting kicked out of prep school wasn’t worth the risk.

Normally.

But these were special circumstances. I had opportunity thanks to Gil and Lew, motive, thank you very much Mr. Taylor. And I had an ace-in-the-hole, courtesy of hooking up with a pretty, but already-getting-on-my-nerves fifteen-year-old freshman, two weeks earlier. (I had similar problems as Brenda on my read-through, and I think her analysis of it is a lot more effective than what I could do. So...see above!)

I slipped around to the back of our teacher’s house and found Gil waiting for me.

“Door’s locked.” His breath was visible in the cold.

“I’ll open it,” I said.

Gil gave me a classic Gilbert and Lewis dull look. The two of them might as well have been brothers, both with Nordic good looks, (Watch the double-use of "look" here.) several inches over six feet…and not too bright.

“I’m going to open it,” I repeated, taking out my tension wrench and wide-tipped pick.

Gil’s jaw went slack, mouth hanging open slightly before he closed it. “I’ve seen this shit on TV. You’re going to pick it?”

“Yeah, if you shut up and let me concentrate.” (I like this dialogue.)

The doorknob turned loosely in my hand. Broken. So, only the deadbolt to deal with. Slipping the tension wrench into the lock, I pushed my rake all the way to the back of plug. The lock turned, (added comma) and the bolt slid back.