When students forget to bring in their books it is not possible to work with them, specially if your class was planned to use the book.
It is specially frustrating when they keep forgetting their material.
Yesterday, when they asked me to play soccer with them, I told them that I had forgotten the ball.
The ball is a very important thing when playing soccer, without it we cannot play. It occurs the same with materials like books.

Now they brought books and a ball! I think they want to play instead of study.