I feel pity for students who go to school idling around during lessons and not doing given work. They are not only wasting the teachers’ time but their own time as well. They are the most selfish creatures in the world to waste their parents’ money.
When things have to be done, do it.
If you are there for a purpose, make the purpose valid.
When you are at school, make full use of the time to study hard and absorb as many things as you can. Even if your absorption power is low, make sure you make efforts. If you do not want to study or do assignments at home, finish them during lesson time.