Hey mama! It must be tough to see your LO cry and not being able to adjust. I know the feeling as I had my boy cry for 2 whole months as I left him to go to work - really difficult to have peace of mind the whole day!
I found that if I don’t turn back after saying goodbye, it gave him more reassurance that I trust the people whom I’m leaving him with. The whole process of getting used to a new class, new teacher, takes time and yes while it’s painful to watch and experience, it’ll pass for sure. You could have short conversations with the teacher when you leave your little one there too to show him/her that, “hey, mama and her are friends, see?”
I hope this helps. Take care okay and know that you’re not alone.