27-month-old’s first day at Montessori went badly — what would you do?

My son is 27 months old and today was his first day at Montessori. He was there for 2 hours. The first hour actually went pretty well, but during the second hour he became really upset, cried, seemed frustrated, and kept pointing toward the door. He even pulled his teachers hair and slapped them.
When I went to pick him up, I saw him outside with the rest of the kids where he was trying to hold his teacher’s hand, which honestly made me emotional because I think he was looking for comfort/reassurance from her.
I’m also worried about his speech and language. He does have some words/phrases, but I feel like he may be behind other kids his age, and I’m already getting him support for his speech/language.
The teacher suggested that we continue coming for 2 hours a day for the rest of this week to help him adjust before increasing his time. When I picked him up he seemed so scared and I never saw him like this before. Before Montessori, he was with me and my parents at home, while I worked from home.
Is this a normal reaction for a 27-month-old starting Montessori, or should I be concerned that he’s struggling this much?
I know the first day can be hard, especially since he woke up at 5 AM today instead of his usual 7–8 AM, so I’m wondering if that played a big role too.
I’d really appreciate hearing from other parents whose toddlers had a rough Montessori/daycare transition. What did you do, and how long did it take for your child to adjust?