If my 13 year old's phone goes off at 9.30, will he miss homework updates in the class group

My elder son is 13 and his class has a student-only group chat. It is useful in theory: who has the worksheet, what page the maths homework is, which day the project is due. In practice it also runs till past 11 with jokes and stickers, and he keeps checking it in bed. I want a fixed time where the phone goes out of his room, probably 9.30. His objection is that the actual homework information sometimes comes late at night, and he will be the one who turns up without it. I would like to know how this works in other homes in the ordinary sense. Does the important information really come late, or is that the argument every 13 year old makes?