There is no excuse for this
It doesn't matter what your age, you should know that buggering up other people's computers is NOT GOOD. It's as if one suddenly decided to see if they could make explosives at home and then decided to try them out by blowing up their neighbor's house (when they weren't home), just to see if it works.
These people cause a lot of damage and expense to others. In some cases, they even could cause injury or death (such as an attack on NHS or someone similar preventing proper treatment because they couldn't access medical records). Punish these little buggers. They don't need to go to prison for 20 years, necessarily, but a little quality detention time and a lot of forced community service (perhaps base the amount on the estimated amount of damage their software nasties did) might help curtail the urge to "try it out for real."