Q: I have a student in my class who still gets upset every time his parent leaves the classroom. Is it very wrong to have the parent sneak off after she says goodbye - since the child won't let his parent leave the room if he realizes she is leaving?
This really is not a good thing for the child's parents to do or for you to support.
For many reasons, a teacher needs to build trust between each child and herself or himself. A child who's suspicious and wary of his teacher won't feel safe, settle in, and learn as effectively as if he trusts his teacher. Learning involves some risk-taking. It's easy to fail to understand or master something, and suffer the resulting embarrassment. A child isn't likely to go for it unless he trusts that his teacher always has his best interests at heart
and can be counted upon to be there for him. If you were to betray the boy by looking the other way while his mom or dad slips out, you certainly wouldn't be building trust.
This little boy's parents most likely want him to trust them, too. Trust between parent and child is fundamental to mental health. Love and self-confidence grow from trust. You say this little guy "won't let" his mother or father leave the classroom. He doesn't have the power to prevent them from leaving, so I'm guessing that you mean he sobs, throws a tantrum, sulks and pouts, or in some other way shows distress. Are other children upset about the child's unhappiness? Often the group takes this sort of thing in stride, but the teacher is troubled by it. This can be because it revives feelings she herself had as a child, or because feeling unable to make a child happy understandably causes her to feel upset.
Do you have an especially empathetic child in your class? He or she can be given the honor of "taking care of" the boy with the separation problem - holding his hand, playing with him, sitting next to him. This can become one of your class jobs, like watering plants or passing cookies, till the child no longer needs the support. Then, everyone is learning to be nurturing, which is not a bad ability to have.