Adachi and Shimamura happened to meet each other on the second floor of the gymnasium as they were skipping class. Eventually, they started seeing each other more and started playing ping-pong together.
We stayed pretty quiet
whenever there was class.
Nos quedamos muy calladas
cuando hay clase.
Cuando tienen clase 
nos quedamos calladas.
Quando c'è lezione non facciamo tanto rumore.
Ficávamos quietas quando tinha aula.