First, please those of you saying that if you can't leave an (in my case) 13yo for a couple of hours you've done something wrong, please remember some of us would give anything to be able to safely allow that 13yo the independence. My 13yo is years away from being able to be left for more than a couple of minutes.
His 9yo brother though, even though he also has SEN is far more capable of being independent. Thankfully his school seems a lot more willing to allow the children independence than seems the norm nowadays. They allow children to walk/cycle home by themselves from year 4 and this is something we've built up over the last year, steadily increasing the distance between where we leave/meet him and the school (which he cycles to/from after doing a cycling course which is kind of pre-bikability). He can also go to the shop on his own and is happy to be left for 20min in the house while the dog is taken for a walk.
Unfortunately I seem to be a bit of an outlier here, possibly because I'm an older parent and grew up in a time when it was very common to spend hours on my out of the house. We actually had one busybody report us to the school for leaving the 9yo for 20min while the dog was walked. Good thing the headteacher is the sensible sort who encourages independence in the pupils. (And that we'd had discussions with her on how we were going to start building that independence over this year).
As for my childhood, I was walking to the park, shop etc with my similarly aged cousins (London so lots of traffic) from around 7. Moved out of London at age 8 and then was walking to/from Junior school, picking up my younger sister and her friend from Infants on the way. Come senior school I was walking the 3 miles to/from school in all weather's from day 1, and we finished a lot later than most schools finish now, in the middle of winter it would be dark by the time I got back, especially I had had detention. At the same age I was cooking roast dinners on a Sunday.
As soon as I turned 13 and 9months, I got a paper round plus working Sat/Sun in the newsagents (for the princely sum of £1/hour). Around the same time I started babysitting for local families, including overnight (for police officers no less)
The day I turned 16 I applied for a part time job in the local supermarket (and started about a week later). By about 16 and half I was working 30hrs/week as well as going to college full time. I was contributing to my families household expenses, buying my own clothes, paying for my nights out.
At 18 I lived in my own flat with a baby, thanks to being taught to do the things needed to be independent, despite having undiagnosed ASD and ADHD, I was capable of running my own household. Of working full time, and being a parent.