I would like to use connection from PowerBI to Office Forms, but I don't know, how create this connection. I'm teacher too :-) I'm very interesting about PowerBI and how use it at school.
Head on over to https://powerbi.microsoft.com/en-us/ and sign up for your account. If you already have an Office 365 account with your school, use that to just sign in. Once you've logged in, you can start importing data from Excel files from OneDrive using the import/connect function (bottom left of the screen after you login, click on the arrow). Connect to your OneDrive account, and choose your Excel file.