<p>If you finish a section extremely early (Math), and you use your time on another section (probably CR), would anyone find out? This is all hypothetical by the way.</p>
<p>Good proctors walk around and watch while everyone tests. Each section has the number of the section in very large, bold font at the top of every page so it would be pretty obvious to a proctor with half a brain.
Also, any student around you might happen to look up and see large areas of printed text (short stories) on the page you’re on rather than diagrams of triangles, and I would hope most would do the right thing and report the questionable behavior. I wouldn’t recommend ever risking it because doing so would have very serious repercussions. Your scores at least would be nullified and colleges you send and collegeboard scores to would be informed you had scores canceled for cheating. And there’s a risk you could wind up having everyone’s scores in your room invalidated, which I doubt anyone would appreciate…</p>