Edtech is a growing space, but a very difficult one to work in (my own experience as founder of letsgeddit.com taught me that). The best solutions seem to target teachers with better tools than they're used to, and expand on them as channels to reach other stakeholders in education (parents, admins).
Notable companies taking this approach include:
http://www.classdojo.com/ - ClassDojo, which gamifies classroom behaviour management is and is incredibly popular with teachers.
https://www.remind.com/ - Remind101 (now Remind), helping teachers communicate with students, parents and other stakeholders.
http://www.showbie.com/ - Showbie, a document management, submission and grading platform.
Another interesting take is by snapping up some part of the curriculum and providing adaptive learning software geared to that (Math and English are popular), like Front Row (math): https://www.frontrowed.com/ and NoRedInk (english) https://www.noredink.com/
There are also platform approaches like Clever: https://clever.com/ and Edmodo: https://www.edmodo.com/
Finally, there are the more niche 'enterprise' tools platforms like Securely which help lock down school devices, and Panorama who provide school and district level suervey information on student wellbeing.
