[ethan]

If this was on my homework, it'd probably be because it was accurate. I'd also probably be aware that I half-assed the assignment before I got it back, and would be expecting at least the bad grade if not the comments. I'd work harder on the next assignment, but that'd also be true for a bad grade and a "see me if you need help, you can do better."

I didn't do all that much teaching while I was in grad school, but I did a fair amount of grading/tutoring during undergrad. (The tutoring was basically TA office-hours, usually 4-5 students at a time, sometimes up to 10 or so.) This being the first assignment, I might opt for just giving them a bad grade and a note saying they should come see you if they're having trouble with the material. If it happens again, then I think you can start in with "this is unacceptable." I think this approach is less likely to end up with them resenting you.

Some people can handle criticism, and some people _really_ can't. I've tutored people who would break down crying when a problem gave them trouble.