At the gatherings available to me, helping the weak singers/players is my role. I am our sturdiest musician. This works well for us and would not be a practical approach in a one-at-a-time group.
I have been surprised at how much my playing has improved by carrying others. Even if I wasn't getting better, the pleasure of helping others grab the music and run with it would be well worth my effort.
So, around here, the bad singers go near me.

I have a question concerning the one-at-a-time type:
How do weak musicians learn solid timing and pitch by practicing alone at home?