[waterhouse]

I'm not familiar with exactly what teachers do these days, but I feel like it's a stereotypical teacher behavior to notice students who look like they're not paying attention—in whatever way, be it staring into space, reading an unrelated book, etc.—and call on the student and ask them to explain what they were just talking about. I'm not sure whether that's a good or bad practice, but it does fit the bill of "immediate correction" that could straightforwardly be applied to students looking at a phone.