The book "Rupee, the Hundredth Sheep". "Adventures in the World of Nightmares" by Ruzanna Danielyan

David is very scared about going to school for the first time and can't sleep because of it, so he starts counting sheep. When he reaches the hundredth sheep, Rupi suddenly appears in his room. She takes David with her to the Nightmare World to help him finally fall asleep. Here, David goes through the Relaxation, Imagination and Adventure rooms one by one to get rid of the thoughts that keep him awake. Unfortunately, his fears are so many that he can't forget them. He needs to go through the last door, which leads to the Confrontation Room. Will he be able to overcome his fears...

This story is about overcoming childhood fears, in this case, anxiety caused by going to school for the first time. The author is a teacher.