I am assuming that he could still have a chance providing we get his head down now and find a good tutor or tuition centre which can be highly recommend and has a very high and guaranteed success rate.
There is no such thing as a tutor/tuition centre with a guaranteed success rate. Nothing can be guaranteed as far as 11+ goes. Even if you find a list of tutors, they will most likely be fully booked by now. I'm afraid I can't help you with getting a list of tutors as we did 11+ DIY.