Oxford University Summer CampsWatch
The University itself runs the UNIQ Summer Schools which are free and open to all Year 12 students in state schools in the UK. As far as I'm aware, this is the only programme that is run directly by the University itself. However, a number of other legitimate organisations use the university facilities (and staff) for their own summer schools. The Engineering Trust runs some of their Headstart summer schools in Oxford (also for Year 12 students, although they are not free for most students) and I think the Sutton Trust might also run a summer school in Oxford for Year 12 students from disadvantaged backgrounds. Then there are a number of private companies that run summer schools in Oxford such as Oxford Royale - I don't know anything about their quality but they are very expensive so personally I can't see how they could be worth it.
The course allowed me to study subjects not offered at my school, or areas which aren't covered in such great detail (experimental psychology and medical biology). All of my tutors were educated at Oxford and were either current post-graduate students or teaching (they all had their PhDs - I am aware this does not measure how good someone is in terms of teaching, though they were very competent and were able to explain things thoroughly and easily).
Additionally, whilst i loved staying there and visiting the city, it helped me see that Oxford really wasn't for me - which is very important for someone who considers applying there.
Granted, during the two weeks it was impossible to cover a massive amount of content, but the assignments and workshops definitely kept us busy and entertained - in a good way.
I think if you choose to do the summer course you should do it because a) you want to study a subject you have interest in and would potentially consider it at uni-level b) you want to see whether you like the city/uni or not, and c) you'd like to meet like-minded people and step out of your comfort zone.
I'm not saying that such summer courses are a necessity when applying to Oxford or any university for that matter, but I just thought I'd say that if you have the chance and the funds to attend such school I'd totally recommend you do so - I can only speak for Oxford Royale though (and no, I'm not sponsored :P). I've heard from my friends that other summer schools they attended weren't good at all, hence why here are my 2 cents.