Three year old having a hard time in preschool EDITTED!

My son (4 in a few weeks) just had his first day of pre-k.

He was in daycare as an infant, but once my second was born (12 months apart) I stayed home. He’s very close to me and his sister. I knew he would have a hard time adjusting, but it seems the school doesn’t really know what to do, and it’s only been one day.

When I went to pick him up his first day, his teacher said she would call me because she needed to talk to me. I was the only parent she said that to, so I knew it was bad.

She called me and told me he cried the first hour, and kept trying to leave the room. He said he wanted to go home and see his sister. His teacher brought him to the hallway (there’s two teachers) and he was finally able to calm down, and he enjoyed the rest of the day (class is 2.5 hours)

They told me they don’t know what to do when he gets upset and asked me what to do. I really don’t know. He’s generally a happy kid so idk. I’m worried he won’t be able to adjust.

**edit- a lot of people are saying that they did know what to do- I am not implying that they didn’t know what to do, but they literally called me and asked me what to do- and my response was “I guess just take him in the hall since that worked the first time?” I am wondering if anyone has any suggestions as to what I can tell them since they really don’t want to take him in the hallway, which is understandable, there’s two teachers with 12 students, so one can’t be in the hallway with him****