It would seem that some pertinent facts are missing (or blatantly concealed) in this question.
Where were you when the assailant picked up your bag and dropped it? Why didn't you look in the bag immediately, especially if you had a laptop computer in it? Why didn't you report the incident immediately, before you left school? Why have you identified the person as someone that you're "sort of friends with"?
What truth are you hiding? Your explanation of the events just doesn't stack up, especially considering that your question reads: "Kid in school purposely broke my laptop?"
Under ordinary circumstances, an ordinary person who had a $1300 laptop in a bag that was dropped on the ground by someone else would react very differently than you did. A regular person would immediately check on the laptop. A regular person would immediately report the incident to whoever could hold the assailant responsible for his actions.
Schools these days tend to have surveillance cameras. Are there any surveillance cameras in the area where you were when this attack happened?
How did you earn $1300 to buy a laptop? How old are you? How old is the attacker? What is the story behind this story? Before a rational person can assess this situation and assign responsibility, all the questions in this answer need to be answered truthfully. Any school administrator, parent, cop, jury, or judge worth his or her salt would need that information in order to dispense true justice in this case.