that sounds like a dumb law, does that only apply to cp?
what if some 16 year old steals his dads gun and go shoots someone? is the dad responsible for that?
Not really. In that case, ownership over the weapon isn't the case; It is the possession and the person possessing it.
With child research, the owner of the device is at fault. The parents could easily be evil and try to evade being charged by planting on their son. It's immoral and a complete richard move, but that's the way the law works.
The parents are the legal guardians. They own the computer. They pay the phone bill. It's their device, and therefore, they are at FULL responsibility. I'm guessing in OP's case, they called the local police or something. In reality, they could be brought to court if somebody wants to get legal and sue