Log out and log in

Open the creative cloud app.
For this it's pretty important you get the creative cloud for desktop app.
https://helpx.adobe.com/download-install/apps/download-install-apps/creative-cloud-apps/download-creative-cloud-desktop-app-from-web.html

Install the app.

sign in with your school credentials.

In my district we have access to all adobe apps when we sign in with our school email (we have to use the "continue with Google" option.  It's easy to pick the wrong google account if you have more than one and have "autofill set up on your browser.

NOTE:  If you subscribe to photoshop on a personal account (like I do)-- sign out from it before you do any of the school related stuff.  This really is of no concern or worry if you are using a school computer. You cannot have creations from your personal and school account show up at the same place at the same time. 

Below is what my personal CC home page looks like. 

This  is when I log into CC using my school credentials.

I generally do not install Adobe apps on my home computer that I do not subscribe to.  Adobe illustrator for example:  I could install it on my personal computer if I wanted But I don't have much free tiime during the school so I don't bother with it. 

This is not an answer to your question, but you might be interested in the new Invite To Edit feature.  Some of us helped test the feature, and I thought at that time that it would be a useful tool for teaching.  Open a file and click on Share, and then Invite to Edit, and you can edit the image while the invited user(s) see the edits on their screens from anywhere else in the woprld with a half decent internet connection.  You need to use another app like Whatsapp, to talk to each other.  It worked great, but at the time we were testing, there was no way to lock the other user out. i.e. they could wreck the image from their end if they so wished.