The obvious answer might be: leave the boy alone. Let him make his own decisions. But teenage sons and daughters don't always know as much about the world as they think they do, and your reasons for wanting him to have a go should at least be listened to.
You, presumably, know that it's a jungle out there and an Oxbridge degree will put you ahead of the crowd; that networks you build up at Oxford or Cambridge can last you all your life; and that while other universities are shoehorning students into full lecture halls, Oxbridge undergraduates still have tutorials either one-to-one or in small groups.
How, you think, can your son refuse to try for something so obviously educationally superior and career-enhancing? But he hasn't been thrilled by what he has heard about Oxbridge, and sees no point in putting himself through an admissions system at which, he believes, he'll almost certainly fail. Maybe he has told himself that it sounds like too much hard work, or that only geeks go there, or that the social life of Bristol or Edinburgh sound more fun.
Whatever is in his head, you need to know more about it. What exactly has put him off Oxbridge? What exactly is the school's view of his chance of getting a place? Is there anywhere else he wants to go? What is he hoping to get out of university? And does he realise that getting in to Oxbridge is always a bit of a lottery - and there's no shame in failing to win the lottery?
If you can open up a dialogue, maybe you can draw his attention to some specific, practical reasons why Oxbridge is at least worth a try. If, on the other hand, he has good reasons for not wanting to go there, you will have to respect them. To keep up the pressure after that would be to make it clear that it's not his ambitions that you're dealing with, but your own.
I graduated from Cambridge last summer but when I was in the sixth form I was half-hearted about applying. My advice is to encourage your son to visit Oxford or Cambridge over the summer to get a feel for the place, and then maybe apply in the autumn. If he is offered a place he can always turn it down!
Jennifer Burns, Cardiff
Taking him on an informal visit to several of the colleges during half-term would be a start. Obtain as much information as you can about the application process, and if he is interested, start preparations immediately. To have a good chance of success you need to prepare well and in plenty of time.
Ann Nee, Kent
I managed to get into Oxford with just 5As and 5Bs at GCSE. How? By being passionate about my subject (PPE), engaging in lots of well-chosen outside reading, writing a genuine personal statement, and practising at interviews to feel at ease. Was it worth it? Absolutely, I had the best three years of my life - socially and academically. Since I left Oxford five years ago, my organisation has helped almost 6,000 people with their applications, so I have met a large number of students who have been written off for Oxbridge by their schools but who went on to win places at Oxbridge.
James Uffindell, Oxbridge Applications, London W1
Next week's quandary
Should parents offer bribes to their children to get good exam results? We've always been against it, but all of our daughter's friends have been promised rewards for good GCSEs - some quite big sums of money, and one even a car - and she seems to be the only one left out.
Send letters or quandaries to Hilary Wilce, to reach her by 9 May, at The Independent, Education Desk, Independent House, 191 Marsh Wall, London E14 9RS; or fax 020-7005 2143; or e-mail firstname.lastname@example.org. Please include details of your postal address. Readers whose letters are printed will receive a Berol Combi Pack containing a cartridge pen, handwriting pen and ink eraserReuse content