I'm not familiar with that variety, but roses normally recover very well from hard pruning. I would make sure that none of the sprouts are coming from below the graft, if it is a grafted one, and rub out any that are.
Note that some climbing varieties won't bloom for a year after such a pruning. Tell your son that he needs to learn a bit more about roses before he prunes again. :)

welcome to GoY.
as Tug says they do normally recover and go on to flower well.

If it is a climber ask your son to tie in any new shoots to give it the best chance of flowering this year. New growth encouraged to grow as close to the horizontal as possible flower better. Do you have 'wires' fastened to the wall?

I have a beautiful but lethal orange rose which could take an eye out because of it's thorns. When we got a puppy I cut it right down to the ground and in six months it was flowering again. I don't know if it's a climber or a rambler but it reaches over six feet tall.

Fazy, I can empathize with you! My son, who lives 130 miles away, turns up every now and again to do a few jobs in the garden He is very willing but I find I have to stand over him and direct proceedings as he hasn't the foggiest idea about gardening! So I suggest that when your son comes, you do the same. It saves a lot of grief and we are both happy at the end of the session.