I worked for a charter school in the era of obsessive state testing, and there were extremely specific rules that students & staff had to follow during state test days.
One of the rules was that after students finished their test, they had two options: silently read a book or silently put their head down. That was it. No other options. It’s also worth mentioning that there’s no time limit on the NY state exams, so our school gave the kids a mandatory minimum of 4 hours… to answer ~30 math questions. Needless to say, they all finished after about 2 hours, and then I, as the proctor, was left trying to keep a room full of antsy 11-year-olds absolutely silent for 2 more hours.