Well, one of them! Since it's such a big building, there are a lot of entrances, about seven. This is the entrance to the gym. On the right is the box for storing your outside shoes. You have to wear gym shoes in the gym.
This is a students' shoes box. The signs say '1 no 3' and '3 no 1'. That means First Year, Class Three and Third Year Class One. You have to remove your outside shoes and put on your inside shoes. Japanese people are NOT fond of bare feet, either inside or outside. Outside, it's too dirty, dangerous, and in summer, much too hot. Inside, you wear inside shoes or slippers on floorboards or lino, and socks on tatami mats. People are concerned about your feet getting cold from the cold floor. People seem to be a little embarrassed about letting people see their bare feet, or worried about sweat/smell so they leave their socks on. Even throughout the heat of summer, all the school children wear shoes and socks, inside and out.
Each compartment has a large area where the outside shoes are kept when you go inside, and the smaller compartment is where the inside shoes are kept when you go outside.
The stairs. The school is three storeys high - typical in Japan.