What you need for a summer holiday is a great program for teenagers in London.
They took last year's “Discover London” course: non-stressing lessons, a lot of excursions and various entertainments inside the school. Groups of studies are small, sometimes they have combined a couple for trips, but, maybe, better - more opportunities for children to communicate with each other. There was a standard overview of the city, visited the Tower and Parliament, told about BigBen and some even modern sights (such as the Cucumber skyscraper). My daughter liked the tour of Windsor very much: since the residence was working, they feared that they would let the maximum down to the fence - but no, study groups abroad allowed many places in the palace, so we could see a lot!
Special thanks to the teachers: we have a daughter with a lot of experience traveling around the camps, and here she liked the counselors and the staff most of all - they were funny, friendly, with children on the same wavelength.