It's not that uncommon, but it's also not a problem without a solution - most schools eventually upgrade their infrastructure once enough parents complain. In the meantime, the first thing is to talk to your teachers. Many understand the situation and can give you more time or let you submit from somewhere else with better connection, like a classmate's house or a nearby library. If you need to work on Google Docs without internet, download the documents locally to your computer, make your changes offline, and sync when you have connection. For video calls, coordinate with your group to record beforehand or separate the audio from the camera if that helps keep everything from crashing - sometimes calls are so heavy that it's better to have a shorter meeting or schedule it when fewer people are online.