My DS (just turned 12) won't be the first to have ever lied to his parents so I appreciate plenty others have had to handle being told "porkies".
When DS was still not home from school 15-20 minutes later than usual, I sent him a text asking where he was. He replied that he was in the school library doing his homework with friends and would be home at a specific time. By pure coincidence, shortly after his reply, I discovered that he had been seen walking away from the school with a friend. In case it was "mistaken identity", I rang the school library and was told he was not there and had not signed in at any point. I explained that I was therefore pretty certain he had gone to his friend's house so they didn't need to be concerned. I phoned the friend's mum to apologise that my DS had (presumably) turned up and wanted to make sure he wasn't in the way but there was no answer and, when I caught up with her hours later, discovered that she didn't get home until about the time DS left her house and that they could not have got into the house as her DS doesn't have a key. She reckons they had been kicking a ball around outside - in the freezing cold, wearing only a shirt and blazer (but that's another battle!!).
When DS got home - at the time he stated - he continued to lie but, when presented with the facts and given a chance to 'fess up, he admitted the truth. I took a calm and measured approach but make it 100% that this is unacceptable and that the worst part is the lying.
My question to you wise mums, dads, carers and teachers is this: should I contact the school to follow up on this? It is clearly not their fault and I didn't expect them to do anything but I wonder whether I should have a chat to his tutor as this is not the first time (by a long shot!) that DS has lied outright, although the other issues have been completely outside of school. Will it just humiliate DS even more to have school involved and how much should they be aware of what he is like?