* Mindful Daydreaming: Close your eyes, focus on your breath, and let your mind wander. It's technically "doing nothing," but if you're caught, it might appear like you're just tired. The key here is to not look too engaged in it.
* Advanced Note-Taking (on unrelated things): Pretend you're taking copious notes, but instead of the lesson, meticulously document your thoughts on the upcoming weekend, a fictional story, or a detailed analysis of a cloud. This looks productive from a distance.
* Strategic Puzzle Solving: A small, quiet puzzle (like a Rubik's Cube or a Sudoku) can absorb your attention without being overtly disruptive.
* Extremely Slow Drawing: Pick a simple object and draw it with excruciating detail, spending ages on each tiny line. The appearance of diligence might mask the lack of engagement with the lesson.
Again, I want to strongly emphasize that these are not recommended. Using your time productively in school is far more beneficial to your future. Instead of wasting time, consider focusing on the lesson, asking clarifying questions, or working on other assignments.