@1forAll74
Although it was many years ago, my daughter was a bit upset and clingy when going into school intitialy, crying etc. The teacher at the door, had the right ideas. she said, don't worry, just go now, and don't linger,, your daughter will be fine in a few minutes when the school day starts,, and this she was. No messing about, as I am sure this happens a lot with some children.
Agree with this, don't linger, hanging about and peeking in the classroom because you are anxious, although well intended, feeds their anxiety, it confirms to them there might be something to be anxious about. The teacher will contact you if there is an issue beyond the normal settling in.
Ds was the same when he started, first couple of weeks were fine, then he had a bit of a dip. Think it is pretty normal.
Your job is to try to talk about what she did that day, sound genuinely interested/impressed/reward her, if she had any specific problems with other children etc and if she did how to handle them (she should tell the teacher) and step in if the problems continue/escalate.
To get them talking about the day start by casually asking very basic but specific questions - in the car home/on walk home/when they are eating their snack/dinner. Where do you go for lunch? Is it far from the classroom? What are the tables like? Who did you sit beside? What did they have for lunch? Did you draw anything today? What colours did you use? Did you learn any letters today? Stop when they get bored so it doesn't turn into an interrogation.