One person's experience does not always match another's so we can both be right. If the bands concerned are happy to support each other then I think such arrangements benefit all concerned. As a teenager I played in a youth band and whilst I didn't make the grade those people who played in the end chairs seemed to, the Band Master would tell us about the various people that had left us and moved directly to join a Championship level Band. Locally what I've seem is what I've seen, there will always be a few that make the grade and there's no shortage of bands happy to take those who don't quite make it. The biggest problem is keeping the youngsters playing; there are so many other demands on their time, etc., and it's also important to support the weaker player: not all can play at the highest level but we and they surely must come to terms with that and take pleasure in their achievements. For those in training bands then, subject to ability and local agreements, etc., I'd suggest visiting others and deping for them was a good idea. Indeed, even if you have outgrown them, supporting a training band is a good idea in that it's both good for society and you'd be surprised what's there (musical and other) to be learnt, rediscovered or just seen from an alternative perspective.