There are more ways for you to monetize your FB group, although in this case, that monetization won't be direct as you can't make a profit solely on the group, and you'll need to do some other activities that will be related to it and that will bring you money. But, if you have a pretty big community in your group, you can use it for attracting some influencers and establish paid partnerships where others would get a chance to advertise in your group. You could also use it for selling your own product or service related to the educational niche, as it would allow you to make higher conversions.