The role of parental responsibility is a valid but separate matter.
Kids can sign up to social media from a friend's phone/ computer/ tablet, from a library computer etc., and self-certify their claimed age. They can get phones (without cellphone contract) from other people without their parents' knowledge.
Kids can sign up to social media from a friend's phone/ computer/ tablet, from a library computer etc., and self-certify their claimed age. They can get phones (without cellphone contract) from other people without their parents' knowledge.