With regards to activities that requires physical movement and partnered training for children aged Five to Twelve, we recommend, you will require one adult for every twelve children, it is worth pointing out that, where you have groups of mixed ages, you must have the right level of supervision based on the average age of the majority of the group.
Now, who are these supervisors? This is another difficult area, because unless the adults are the parents or legal guardians of at least one of the children involved, they need to have suitable supervisory qualifications. There also needs to be enough supervisors to cover necessary breaks or for the adults to deal with an emergency, Do not confuse Supervisory roles with Instructors – Supervisors can only supervise and only under supervision themselves, Instructors can carry out both supervisory and Instructor positions.
The best advice is to have plenty of supervisors. Make it into a community event where people can meet while still allowing the young people of your community a little freedom. At this time there is no legal statutes having a class size over Twelve but under Thirty students - A good place to find further advice, is your local Council office as they can at least signpost you to a suitable community advisor and any Local Legal requirements.