London's Centre for Young Musicians, or CYM, is a Saturday music centre for children up to 18 who play an instrument, currently run by Stephen Dagg. Anyone other than an absolute beginner is eligible for it, although there is an audition process.
A standard timetable consists of a 30-minute lesson (some students have a 45 or 60 minute lesson), choir, musicianship, and where applicable, an instrumental ensemble. It's only until students reach Yrs 11-13 that they can opt out of choir and/or musicianship but many choose to carry on. Other classes include special Grade 5 Theory, composition and various ensembles and band to further their playing skills. An accompanist is available for students to practice with prior to concerts or exams.
Many pupils from CYM also take part in the LSSO (London Schools Symphony Orchestra) or the LYWB (London Youth Wind Band).