In our experience in running the last few shows, the Junior class is very poorly supported. I have recently worked with some of our primary schools in the area spending six weeks running modelling clubs as an extra-curricular activity and, although well supported and some fantastic efforts by the kids, the feedback from the parents at the Celebration Evening was not very encouraging. The main excuse/reason was the expense of the kits, equipment, etc. If a child has parental support and is encouraged at home, as I did with my two kids, they may have crack at modelling as a hobby for a while, but generally, (and it is a generalisation) other things tend to take over, such as exams, schoolwork, friends, etc, etc. I think the issue that we have to take into consideration is that modelling, painting, etc is ostensibly an age related hobby. Im certainly not saying that there arent younger modellers out there, but the vast majority of us are of a "certain age" when building kits, etc was a right of passage which we all did as kids. Just look at the typical average age of club members at the next show..
Society's leisure activities have changed beyond recognition in the last 20 years and modelling, in its many forms, is not high on the list of may young people, unless they have a family member who is involved in the hobby, as it is considered "boring" by most. (I have the conversation regularly with my students!) I think trying to "convert" kids into thinking this is a worthwjile pursuit, would be an uphill struggle. There is a noted lack of dexterity amongst many of our new students, many of whom, struggle to hold scissors correctly (seriously!) and have very little patience for such painstaking work. The end result is just not "instant" enough for the vast majority of our students.
I really do not want to sound negative about the idea, at all. In fact, I fully support the idea of a Young FOM section, as a concept, but, playing Devil's Advocate, Im just not sure that all the hard work involved in setting it up will reap any reward....