How to deal with late or tardy students. There's two different things here: One might be a student who is just tardy on a particular day, and you want to know how to kind of re-integrate them back into the class. The other is for the student who is chronically tardy. For the student, the single student, who is just tardy on a particular day, have a procedure in place for students that they know to follow when they come into the room tardy. Should they come up to you with a slip, a tardy slip, is there a place in the classroom where they should just place that tardy slip? Should they move silently to their seat and wait for you to approach them about the tardy?
Whatever your system is or whatever you most want from them, set it up at a procedure. Explain it to the students. The first time a student is tardy and comes up to you in the middle of your lesson or during the warm-up activity, that's the time to take a step back, take a pause and say "Let me explain to you, class, how you should behave if you come into the class late. You should come in, drop your tardy slip here in the box, pick up a warm-up activity, and sit down at your table and begin". As long as it's clear and it's practiced and it's reinforced, it'll work with students.
If you're talking about a student who is chronically tardy, who is tardy multiple days in a row ever week, when you're at three or four tardies, you start with a one-on-one conversation with the student about why they're tardy. At the elementary level, this is really out of their control if it's the beginning of the day and they're tardy. They're being brought to school by their parents, and that's an issue to discuss with the parents. At the secondary level, that could in fact be the student who is just not coming to class on time, and it is their responsibility. So you have a one-on-one conversation. "What is in the way of you getting here on time?
What is happening between your first period class and this class that you can't get here?", or whatever the situation is, start with that personal one-on-one conversation, and see if it can be taken care of in that way. If it cannot, the next step is a call home. You want to reach out to the parents, you want to find out what's happening, whether they know if the student's been tardy, and what information they might have for you related to the student's behavior in coming in chronically tardy.
When you're talking about six, seven, eight tardies in a row in a very short period of time, and you've called the parents and you've talked with the student and it's still going on, now is the time to bring in the administration. Now is the time to have a meeting with the student, administrator, and yourself-- possibly other teachers who are also experiencing chronic tardies from this student-- the parents, maybe even the counselors to get involved in figuring out what is going on there, and what needs to happen to get the student to class on time. So those are some ideas about dealing with tardies in the classroom.