Recent research suggests that you will only find provision for under 18s in around 50% of churches in the UK.
If you reduce that to provision for 11s to 18s (youth) your chances are reduced to 25%. Starting up in youth ministry can be hard work and discouraging, but, if the figures are right, then 25% of churches providing something for children have nothing for post-11s. What those children do at 11 is open to speculation, but I suspect it is a mixture of moving on to other churches or staying at home.
Critical mass?
You often hear the idea that young people need a critical mass to feel they are part of something significant. Unless you have at least ten there is no point starting up. My mind goes back to two 15 year-olds who came to Keswick youth meetings — they were from one of the Outer Hebrides islands and were the only two young people in their church. They were led by someone in his 50s and they loved it. They were serving in the church, being well taught and encouraged to engage in discussion and prayer.