Teaching is difficult enough from a personal performance and logistical standpoint that there is low hanging fruit in simply helping teachers be their best professional self.

For example: I have approx. 200 high school level students. If I assign them to write one page I have just given myself 200 pages of assessment to complete. Assessing writing is more cognitively demanding than simply reading 200 pages, so if I can read and provide feedback on each page in 3 minutes - working non-stop - I have 10 hours of work. I have 5 hours of prep time per week which is primarily used for preparing the 7 hours a day I spend actively in class with students. Given that we don't complete just one assignment per week - you can see the logistical difficulty.

I teach english. There are commenting/notemaking tools in almost every online word processing toolset, but none of them are streamlined for assessing writing (i.e. providing rubric based feedback, rapidly annotating with custom or pre-created notes, allowing for layered annotations to identify different structural features of writing). There's opportunity in figuring out what teachers already do and slash the time required to do it.