advice for dividing small groups
1. Breaking students into small groups is never easy.
2. Breaking students into smaller groups when groups grow is never easy.
3. You can lessen the pain when you use the term "launch" instead of "split" (i.e. "we'll be launching a new group out of this group because great things are happening in here."). Launch can be positive. Split can be negative.
4. Let small groups know from the beginning that "launching" new groups is an exciting thing. Tell them it's a real possibility when the size of the group reaches ___ number of students (___ = whatever you decide on).
5. There will be a natural decline in intimacy when students start a new group--that's normal. But, if the groups just started 2 weeks ago, most likely your groups haven't begun to scratch the surface of intimacy. The sooner the better is the time to launch the new groups.
6. If your groups are "open groups" (meaning students can be added as they arrive) you'll always face this "problem" (what a great problem to have). As students in their small group grow spiritually, they will most likely reach out to their [lost] friends and invite them to join a small group. The only that I know to keep the numbers small and not disrupt the small groups is to change your philosophy to a "closed group" (meaning that once a group starts, it stays that number until the quarter/semester/school year is over (whatever you decide on)...and when a new student come, the student begins in a group that isn't "full". There are pros and cons to every youth ministry strategy.
7. Don't really have anything else to write here for #7...it's getting late (it's midnight) but it seemed like have 7 points would be a cool thing. Not sure if any of this is helpful...Oh, here's a thought; term your changes "experiments" and be willing to allow them to fail (who cares if something goes wrong--if it was an "experiment"). Learn from your experiments and begin to develop principles for small groups that you're passionate about and/or ones that work for your particular youth ministry setting.