Trying to maintain some sense of perspective here and not fly off the handle!
DS is largely well behaved, responsible and mature. However he developed a new friendship group some months ago that his school has raised concerns over. His behaviour at school started to dip (nothing major) and we told him this had to improve or he would be grounded. His behaviour is school has improved and he's been getting his head down with revision (although could do more!).
All has seemed good, except we have now discovered he recently stayed at his father's house with a friend, whilst his father was away, when he'd been expressly told this was not something we'd permit. He lied to me that he was staying at a friends (I dropped him there!). We only discovered when his dad came back and found some food containers in the recycling that weren't there before. No evidence of foul play or that others were involved - neighbours haven't complained about noise and I don't believe it was a party or anything. They obviously tidied up after themselves! The amount in the recycling would verify it was only 2 people's waste. He says they just had sonething to eat and stayed up late playing on the PlayStation. I have a hunch they were vaping (school raised concerns about his friendship group in this respect).
Whilst seemingly no major harm done, I am livid that he lied to do this behand our backs. Interested to know how others would handle this. I am thinking of grounding him but no idea how long for. Not really ever had to discipline him much - usually just talking through consequences and setting out future expectations with threat of luxuries taken away/grounding has been enough. But this has crossed a big line for me. His dad is going to put an extra lock on his door when he's away and DS is with me, so it cannot happen again, but he needs to learn a lesson here about trust.