Skype for Business was replaced by Microsoft Teams.
Microsoft Teams can be used as browser version or as desktop application (also for Linux). In addition, apps for mobile devices are available. Teams is integrated in the Microsoft 365 environment. Thus co-operative work like working together on documents at the same time can be done with integrated tools.
The co-opearation of students and teachers is addressed by the available education version. More information can be found in the following quick-start guide: