Llama Llama Misses Mama by Anna Dewdney.

It’s Llama Llama’s first day of preschool! And Llama Llama’s mama makes sure he’s ready. They meet the teachers. See the other children. Look at all the books and games. But then it’s time for Mama to leave. And suddenly Llama Llama isn’t so excited anymore. Will Mama Llama come back?
Of course she will. But before she does, the other children show Llama Llama how much fun school can be!