What age did you give your kids their own mobile phone?

We gave our 7 year old son his 1st phone this year. It doesn't connect to a network, he only uses it for WiFi: music & games. He can message me using the Messenger Kids App that way. It's taught him a ton of responsibility. I was shocked when I was checking over it (which I do every night to keeps tabs on what he's doing) & saw he created a phone alarm to wake up, one to get ready for school, one for when his bus comes & apparently one for when to make it quiet when he is at school. I was upset he took it to school at first but impressed he was smart enough to figure that one out & do it! I was worried at first but impressed on how he has handled it.