I wouldn't bother. He would essentially doing it purely for ego. Better to invest the time and money in focusing on the degree. Also keep in mind that the first term at uni is generally... "chaotic". Remember the leap from GCSE's to A-Level where you were wondering to yourself wth all of it was about? That's about to happen again. On top of that there is the inevitable fresher's freedom. Is he really likely to be sat at home studying not only however many modules he has, plus extra A-level (redundant) physics whilst everyone else is out partying and socialising?
School held your hand through everything, Uni does not. Don't overload your system needlessly. If it *REALLY* bothers him in the future then there's nothing to stop him retaking them in 10 yrs time when he's established in "life" and has some free time to burn.