Monkeys.

 Monkey teacher: let’s solve this puzzle.

“Are you working on the weekend?”

Monkey student: ha, ha, ha.

Monkey teacher: yes!

Students, this is the correct answer.

“A plus” and banana.

Anyone who wrote “keep working”, fix by tomorrow.

Now, open your colourful books and write “ If you wake up in the morning and think about going to work, you are not a monkey”.