Hi Sal; I can't speak for all schools, but it's much too general to just refer to 'schools' in this context. Painsley School, where both my daughters went up to age 16, has open access to the music rooms for any pupil who is interested, and actively encourages lunchtime and after school music making. My younger daughter spent a lot of time playing piano for unamplified vocalists and singing herself. Music made by pupils was part of every assembly, and the school shows were done without any taped music whatsoever. This included the best amateur performance of the notoriously difficult Les Miserables I've ever heard, with a pit band of pupils to match any I've heard in the professional theatre, and some serious voices in the lead roles. The young man who sang the role of Valjean would have graced the West End stage, both as an actor and singer. The school has 850 pupils, and boasts a 100 piece orchestra, a 100-strong main choir, a male voice choir, a barbers shop group, a traditional music group playing Celtic stuff, a wind band, a jazz big band, any number of rock bands and even a parents ensemble. The Christmas concerts involved virtually the whole school, and were just brilliant events.
Much of this depends on the Headteacher, and the quality of the music department staff. Government education policy has very little effect; some schools will always do the minimum, and some will stretch the boundaries, like Painsley. Oh, and Painsley is not some kind of Performing Arts academy; it's a local comprehensive school with specialist status; as a Science specialist!
Painsley justified the huge time and effort they put into all this by making the link between the confidence to perform and the confidence you need as an adult in other areas of life, and that makes sense to me.
The other area for encouragement (for me) is folk sessions. Check out the average age next time you are in a session. Are we folkies doing enough?