There are a variety of extensions that may not apply directly to students but may make a world of difference when used as a teaching tool. Some of the most useful extensions for teachers are listed below.
Google Cast for Education: this extension allows the teacher to receive screencasts of students' computers. When connected to a projector, students can easily share there Chrome screen with the entire class.
AdBlock for YouTube: This tool is like the one above but it targets YouTube videos and tries to remove any unnecessary ads that are played before the requested video. Again, results may vary.
ImprovedTube: This extension will bring additional customization options to YouTube such as changing the quality of the video, hide annotations, comments, suggested video boxes, and elements.
PollEverywhere: allows audience participation when presenting a slideshow using Google Slides
Share to Classroom: allows the teacher to push out webpages to the entire class (as long as they are registered in classroom) so that everyone is on the same webpage instantly and effortlessly.