I would ask for a meeting with the student and the teacher who referred the student to the program before allowing him back into the program. Clear the air but set boundaries of what is appropriate. I'm glad you didn't take a spill because of an impulsive move by a kid who was acting out. You could actually turn this into something positive if you choose, mostly by letting him know he didn't peeve you to the point that you won't work with him. That being said, I would totally understand it if you asked that student be barred from your program.