It depends on the type of educational app in some cases it’s preferably to have both but there can be the other option. Let’s make a quick overview of apps:
Educational marketplace. We recommend to start with the web, mobile would be a nice addition to have.
Courses and Books libraries as an online database. The best way would be to develop both web and mobile applications. - The web would be beneficial since browsing for courses usually implies that users will be putting their time to research, and for such kind of cases users usually use laptops. - But the mobile applications are critical for the already purchased courses to keep them involved.
Application to inform your students for language, summer, and other schools. Recommended to have Mobile Apps, since this way you’ll make sure that the info gets to students because all of them never leave their phones alone.
Online educational process. Recommended web, since the educational process requires discipline and for that, you want to ensure students are using their laptops and are sitting behind the desks.