Google+ opened to students 13 years old or older. As ZDNet reported, in conjunction with opening Google+ to teenagers Google opened a new Google+ Safety Center. The Google+ Safety Center features a couple of guides to Google+ settings and functions for teens and their parents. The section for teens isn't much more than a basic introduction to Google+ settings, but the section for parents provides some solid advice and answers to common concerns that parents have about their teens use of social media.
In addition to information about Google+, the Google+ Safety Center offers resources from Common Sense Media about anti-bullying practices and digital reputation management.
Applications for Education
If you're considering using Google+ with your teenage students, you might have some parents with concerns about having their children using the service. The materials provided in the Google+ Safety Center could help ease their minds.
Some of the features of Google+ that could be of use to students are screen sharing and document sharing in Hangouts. Those two services could be helpful for peer editing and or peer tutoring. You and your students could also use the Concept Board app in Google+ Hangouts for collaborative brainstorming sessions.