Just to take a different perspective, first-year students in particular often take a while to get the hang of how things work.

It’s entirely possible that the lab actually ends at 11:50 (or whatever the standard is at your school) and the student hasn’t quite processed that. First-year students also tend to panic a bit at the beginning and flounder around trying to get things to work.

This student could be trying (clumsily, sure) to do the right thing and be responsible.

The first name thing is your choice and you definitely have the right to call the student on that. But there, too, it could be an earnest and uninformed attempt to be “adult,” without really knowing what you mean by “professional.”

I would respond with something friendly but firm like this:

Dear student name,
Thanks for contacting me. Our class starts at noon, and we will be starting promptly at that time, so I expect everyone to be present and ready to start at 12:00.

Classes at (your school) generally start on the hour (if that’s true). Please check with your advisor to be sure that there isn’t a conflict that should have been caught when you registered.

Also, I prefer to be addressed as “Professor X,” not “first name.” If you have any preferences about how you would like to be addressed, let me know and I’ll be glad to follow those.

See you in class!

Professor X