That is terrible. At my DCs school they each go into the HTs office to have a final check through absolutely everything and read their reference, and then make a bit of a deal about 'pressing the button!!'
It is a horrible thing to happen, but your DS's whole future is definitely not in jeopardy!
Your DS's school needs to urgently contact all five Universities and explain their error. If they do this, the chances are that most will look at the application again with the new information. When this has happened to students applying to us, we would always do this. I would expect most other universities to do the same.
Even if things are not rectified now (and they should be) there is nothing to stop him applying next year anyway. So the worst case scenario is an unwanted gap year.
I don't know what the legal position would be on this, but I suspect the cost of pursuing that route would not gain you much. I would expect a grovelling apology though
Have you asked the universities whether he can reapply based on the new predicted grades? I would be furious, but I think the first thing you need to concentrate on is getting another application in, if that's possible. Deal with the school after that.
My son applied for universities two months ago, for universities such as Oxford and UCL. Yesterday, he received emails stating he had been rejected for all bar one(still pending), and the feedback provided was that his predicted grades were too low, even though he had very high predicted grades. The UCAS coordinator at his school admitted to sending off the incorrect predicted grades, however my son's whole future has been put in jeopardy. Could someone please provide me with some advice about what action to take as well as some legal advice.