You can include in-app advertisements, i.e. allocating your web space to other businesses to play relevant ads according to the app you develop. It could be games, or e-books or anything related to your educational app or students.
Second, you can receive a commission from payments. This is possible if you are a business owner and do not create an educational app for your own. Whenever a student opts for a paid course, you receive a commission.
Third, subscription fees can get you revenue when a student opts for a premium subscription.