Would you join an online community for people living in the USA?
What about people living in New York? Or perhaps just Manhattan? Perhaps an online community for just the Upper East Side? Perhaps just your apartment block?
At what point do you feel you have enough in common with others that you would join the online community?
It’s crucial to narrow your community’s membership focus to people who share a very strong common interest.
Contrary to what you may think, narrowing your focus to less people makes it easier to get more members. If you’re struggling, don’t try to broaden your focus, narrow it further. Be more specific about who is and isn’t a good member for this community.
You can start an online community for teachers, or teachers in the UK, or history teachers in the UK, or history teachers who use game-based teaching methods. Sometimes, just history teachers will be enough, sometimes you need to be more specific.