Hi @bustawin, sorry for the slow reply! What countries will you be using RACHEL for schools in? We don't currently track usage metrics across RACHEL, but we've heard from our users which content modules are most used in various areas. Often Wikipedia and Khan Academy are the most popular, and of course local content is heavily used as well where we have it.
Let me know which country/countries you're working in and we can connect you to some others who can tell you more about what they use the most!