Karan was of the age to acquire knowledge, so Adiratha sent him to the village Gurukul.In Gurukul, Karan armour & earring were like a curse for him, the children considered him different due to,Not even at bath time. They were always there and they always protected him.
The armor on his body certainly protected him, but it was also a lifelong pain. He could not play with any children because one day, while playing, a child punched him on the armor and broke the bones in his hand.
Because he could not play with anyone, he spent his time in Gurukul in acquiring knowledge and art of weapons.Due to this Karna showed immense skills with weapons. The gurus in his village school felt the classroom was too small a place to contain his talent.They recommended higher education.
Because he listened to the teacher, he went from one Gurukul to another to acquire more knowledge and art of weapons.