Unfortunately, I don't think there is much we can do. Re children, education is always a good thing as is a good clip round the ear if caught. But you will still get the "I'm 'ard so I don't give a stuff" types. Kids is kids.
However, the "Gentlemen" who were quad-biking were old enough to know better anyway. Hopefully their story will make some other brainless idiot think twice before doing the same thing. Mind you, adults have been chased and have run across the 4 lines outside at Ilford Depot before when they were caught spraying trains. They were all adults too. No-one got hit, but they still ran over 4 live lines.
Then there are crossings, you can have all the bells, barriers, cameras, signs etc. in the world, people will still ignore them and either a) get away with it, so that's not so dangerous, I'll do it again or b) get hit. In which case they won't do it again, but that's only one person who has learned their lesson. There will then be a convoluted enquiry and it will be found to be Network Rail's "fault", who will then either close the crossing to great gnashing of teeth from the locals or will have to install more bells & whistles when the labour could be better used elsewhere. Cable theives, money is a great persuader. Even when one of their ilk got fried on c2c a few months back (good riddence to bad rubbish), it didn't stop others doing the same thing yesterday at Chelmsford. If 25,000 volts is not a deterant, I have no idea what could be.
In all this I am not forgetting the poor sod driving the train in any of the cases who now is effected for life.
Maybe as part of the "education" people who have been caught tresspassing should be made to walk face-first into a coupler. If it hurts them at 2mph, hopefully they will think what it might feel like at 80mph. But I don't hold out much hope.