It’s probably best to have a policy of not “friending” current students.
Kids today need to do their homework and get their rest. They don’t need a prominent presence on social media and the burden of staying connected at such a young age. Something is up if teens feel they must be online all the time. Is someone pressuring them? Are they bullied or bullying? Are they sending inappropriate photos? Are they in contact with people they shouldn’t be? Are they aware that their electronic presence is eternal and will follow them indefinitely? It’s too much to manage and too permanent. Unplug and take care of yourselves!