Most churches have separate programs for kids that are this age, and a lot of kids really think it is fun. My daughter used to love her Sunday School class when she was that little.
I would actually be asking questions about who is tending the children while I'm in church service. They could just have a mean teacher, or there could be a bully in class. My son freaked out about his Sunday School class once, and we figured out it was because he was just scared of his teacher. She was very big and even though she really is a kind and loving lady, she intimidated him.
I was pretty worried when he had this reaction about going to his class. (WHAT are they doing to him???) He and I went to talk in private, and were able to let the other teacher know about his worries. "She's just so BIG!!" (I was so embarrassed but also wanted to laugh out loud from relief).
About this drawing: Who is Bibi & why is Bibi crying? Could the child just be sad to leave a friend?