As it is time that they have just entered puberty, they will have hell of distractions. The base of all distractions are girls and comes the other factors.
1)Access to everything
As a child, parents have restricted them in many activities which are inappropriate for their age, once they attain puberty they will start to explore everything they see and everything they are interested and they will experience a sense of freedom which is new to them and they will start to use it, they may not know the consequence or cause and effect of their actions. As soon as something interest them they move from one to another without finishing what they have started. And end up in landing on things which created dopamine in them.
2)Hormones actions
After puberty, sex hormones will start to play the role, those hormones are very powerful in nature, which would keep the person under control.