gText is a new service offering free group text messaging. There are other services that do the same thing, but those services weren't developed by a high school student the way that gText was.
gText allows you to send text messages to groups that you have created in your gText account. Your texts can be sent from your phone or from your computer. By default gText keeps group members' phone numbers private. Group members who want other group members to see their numbers can allow that. Beyond simple text messaging gText offers options for sharing files (although that could consume a lot of space on a phone), sharing images, and sharing calendars.
Applications for Education
I signed up for gText and am waiting for my verification code in order to try it out. My initial impression is that it could be used in a manner similar to what I've done with Google Voice. Text messages rarely go unopened while emails often do. Take advantage of that pattern by texting important reminders to students and their parents.