I teach in a private school. 3 times now (since i have been at the school) the school have appointed unqualified teachers.
They have NO IDEA how to do the job. Simple things such as pacing a lesson just doesn't occur to them and then they have terrible discipline problems because the kids are bored. These kids don't behave badly in their other lessons.
The non qualified teachers don't seem to be able to respect their colleagues and think they know best / sulk if they don't get their own way. They are also frightened of change - if something works once, they want to stick to that plan/ method religiously never mind that the kids have changed so we should be looking at different approaches.
The pgce might only be a year, but in my experience it makes a huge difference.
The idea of putting an 18 year old in the classroom is ridiculous. I teach the 6th formers at my (good ) school, and I have young children. I wouldn't even consider them as babysitters for my kids never mind let them 'teach' them!
Give them 5 years to grow up a little and then perhaps they can try.