Eaglercraft has taken the Minecraft community by storm. It is a groundbreaking recreation of Minecraft that runs directly in your web browser using JavaScript and WebGL, without requiring the official Java edition or a downloaded game client. This means you can play real Minecraft 1.8.8 or 1.12.2 on a Chromebook, a school computer, or any device with a browser.
For visual changes, you can use resource packs, which Eaglercraft supports natively. how to add mods on eaglercraft
The short answer is yes, but not in the way you are used to with Java Forge or Fabric. How to Add Mods on Eaglercraft: The Ultimate
Here is the modern, working method to add mods: a school computer