I've found it's quite environment-dependent for me. When we lived in Switzerland, I once or twice left my then 9 yr old to come home from school for lunch for two hours, let himself in, eat the sandwiches I'd left wrapped for him, and get himself back to school for 2pm. But this was in a densely residential area with a friendly immediate neighbour across the hallway and a couple of others in the next-door building on stand-by in case he ran into difficulties/ got lonely or bored.He's 12 now, and we've recently moved to the US. We now live in a far more sprawling neighbourhood, and only know one or two immediate neighbours to say hi to, who may or may not even be in when I leave him alone. So even though he's now 3 years older, I'm still only leaving him for 2-3 hours at a time.We're both completely comfortable with this: he has a phone, knows where I am and approx when I'll be back, knows what he can forage for snacks (nothing cooked or involving sharp knives), and knows what to do in if the doorbell rings/ there's a fire (in varying parts of the house - what if it's in front of the designated escape route?)/ there's a major water leak/ he gets stung by a scorpion - ok, that last one's probably not a major concern for you :-)If I knew a few more neighbours and their routines, or if he was culturally more clued up on things like dialling 911, I'd be more at ease leaving him longer if needed. But at present, I'm trying to find a middle ground between his previous freedoms/ my fairly liberal views on this, and the culturally-accepted 'but danger lurks EVERYWHERE!' paranoia here that has resulted in things like 12 yr olds having to go to the school toilets in pairs if they need to pop out during lesson time.When in Switzerland, my younger child occasionally walked herself to school or back, aged 5 - this was not unusual there. And I would happily leave her for 20 mins whilst I popped to village shop. But again, this was with my apartment neighbour there so my daughter could wander through to her house if she wanted anything (she never did; in fact, I'd time this sort of thing around a favourite TV show, give her a bowl of nibbles, and she'd never moved before I got back). Plus she's a total Stepford Child, who's spookily biddable and mature.Where we live now, I'd still leave her alone for 20 mins, but there's not really anywhere I could get to and back in that time anyway, so it doesn't arise. I'd be happy leaving the two of them together, aged 12 and 8, for around an hour or so if I needed to pop out - they're good kids who play brilliantly together.These are daytime figures - I haven't yet started leaving them alone after dark, which somehow seems different.My childhood was much like yours: age 9, my parents were postmen, so they left the house at 4.30am and left my then 12 yr old brother and I to get ourselves up and off to school (for me, this was a 5 min walk alone to bus stop, bus for 3 miles, 5 min walk to school through a town centre crossing busy roads). And I would go off with my friends on our bikes for miles and miles and hours and hours, in a time of no mobile phones. We moved house just after I turned 13, so I know I was doing all this aged 12 and under.Hopefully your ex's solicitor will point out that you've done nothing illegal, and may even helpfully suggest that the sort of pre-secondary school training you're implementing is the stuff of responsible parenting rather than the reverse.