Question

How do u tell someone to have a good day when its their 1 day of school

Answer 1

"Have a good first day of school!"

Step-by-step explanation:

I'm not sure if this question is entirely serious but when it is someone's 1st day of school, the proper sentence to wish them a good 1st day of school would usually be "Have a good first day of school!" or a statement with similar meaning: "Enjoy your first day of school!"

Answer 2

You can tell them by
Did you like your class
Hope you enjoyed your first day of school
Etc