I am very mindful that many parents of children engaging in a digital world feel a little out of control at times! There is a lot of informal learning taking place here and if parents are not involved in how their child is interacting socially in a digital world, then it is easy for small things to become big things which in turn affect relationships and family life. Your child needs you to take control...by being involved, showing guidance and setting rules in place.
You can't control the internet and neither can the school for that matter. You can't control the access other families allow their children as we all have different views and values and expectations. However, you can make sure you have clear family guidelines for using the internet such as when devices are handed in at night, shared passwords and pages so that you can see what younger students are doing. Social media like facebook offers guidelines on ages to be on facebook. These are sensible as you need to think about what your child will be seeing and learning about. What is your family comfortable with? Do you know all the social media your child is connected with e.g. facebook, snapchat or instagram etc. You could learn them together.
Vodafone has put out a new site for parents to help navigate the waters: http://www.vodafone.com/content/parents.html
I can't recommend the Get Started page enough!
It is that old saying 'knowledge is power' make sure you know what is going on for your child in cyberspace. If you know how it works then you have the power to set the tone and direction for your family.
Together you are lifelong learners.