.L. I am not trying to be mean when I ask this, but if the teacher helped you with a short good bye did that help? I guess what I mean is three of my children have been to preschool, the first could care less if I was there or when I left, the second liked me to be there but was ok if I wasn't. Now the third one wants me to stay but is a totally different child while I am there. With my first two children we went to Co-Op preschools, they are more family friendly as they are run by the families themselves, along with a certified teacher.
I remember the first time we had a child that cried and screamed when the MOM left. Mrs Schrow took the child to another part of the room and had the Mom leave as the teacher was walking away. As soon as mom was gone the crying stopped, no questions about Mom just a regulator day. Then Dad brought him in and nothing happened at all just "bye Dad see you after school".
This showed me at least that the teacher wasn't being cruel just helping him adjust to a different situation. I do know how hard it is to leave a screaming child when my oldest was in third and fourth grades I stopped into class for my DD Birthday and when it was time to leave the principal had to pull her off me. As soon as she seen me drive away she was fine. I got a call from the school before I was three blocks away.
So I guess the point would be to make appointments with the preschool and see how they handle this kind of situation. You may find that Co-Op's tend to be less strict as to when a parent can be in the room and for how long, as they rely on the parents to help in the classroom monthly.