Google+ is now available to teens 13 and over and with new protections for those teens who join. Some of teens features are
Teens see a warning when they share with “Public” or “Extended Circles”.
By default, only the people in teens’ circles can interact with them and their posts.
Teens are muted if a stranger outside their circles joins the hangout.
The new age restrictions will undoubtedly help Google increase its user base.
Google also built a new safety center for Google+. Visit google+ safety center