It has been brought to our attention by a number of parents that children in various classes have set up viber groups. This allows them to chat with a group via text message for free. It is important that you as parents are aware of this and keep an eye on the content. If children know that you are keeping an eye on their phones, it is unlikely that they will post or text anything inappropriate.
As Viber activity seems to escalate after bedtime, it might be a good idea to leave the phones/iPads/iPods/tablets downstairs at night.