if you tell your kids to write a paragraph about why we did yesterday's lab, they will probably stare at you unless you give them more direction than that (for example: saying that this paragraph should include the goal of the lab, the conclusions of the lab, and how this is connected to the material we've covered in class, or what you've uncovered about the unit we're about to start). if you've done this activity 17 times before, yeah, you can just tell them to do it, but good luck giving them a new, vague assignment and then going to sit at your desk. unless, of course, you want to read 150 paragraphs that start "um.... idk."
also, be super-specific when giving the daily kinds of reminders that you say 50 times a class period. for example, "sit down" or "take a seat." if you teach the darling 14- and 15-year-olds that i teach, you will probably get many interpretations of the words "sit down." they know you mean "sit down in your assigned seat," but they will probably try to impress you with how witty they are by sitting on the floor, on a table, on a counter, on top of their desk, on top of someone else's desk, in someone else's chair, or in someone else's chair with someone else. just say "please sit down in your assigned seat," and you save yourself some headaches. another variation: "keep your hands/feet/backpacks/lanyards/books/notes/entire person to yourself."