Can someone help me

Like I mentioned in my last post my 4 yr old son was left by himself in the class while everyone went to take pictures. His had this same teacher since last year when he was 3 same staff same teachers. I have never had issues with anyone my son loves his class and his teachers. He loves school and cries when I pick him up he goes for 3 hours. Today idk if it was an accident or what ? But for some reason they thought everyone was in line and left to take pictures and a staff found my son by himself in class. Although they always help me when he gets his nose bleeds and let me know if something happens just like today Tomorrow I’m talking to the teacher & staff together to know what really happened. Idk if should continue to take him there? Idk if I should stop taking him to school and wait til kinder (different school) i told my husband it could of been a worse situation he could of easily wonder off and have access to all the doors and leave it’s scary for me as a mother to even think about it right now ☹️