Happend on my Focus ST after my dad had been out in it, rolled down our driveway into the garage door , luckily no damage hardly. Heard the bang and thought something had fallen upstairs in the house , went outside and the focus was sitting snug against the garage door

I usually always have the footbrake on whilst applying the handbrake , & on steep hills / inclines Leave it in gear too - hope your kid gets sorted without too much hassle