Hedgehog in a Backpack

On her first day of school, Alyonka finds a hedgehog in her backpack! How did he get there? The hedgehog just loves adventures and dreams of finding out what school is all about. He is also very curious about where the delicious smell of pies comes from, why the board needs to be erased, what is rustling so loudly in the cloakroom, and why there are so many balls in the gym?