That depends on how mature and responsible your ds is, how long you will leave him alone for, if there are any security concerns where you live, what support he has e.g. neighbours to call on if something goes wrong.
It does rather depend on your individual DC. But i think it is common for children to be letting themselves in after school from year 7 onwards (especialy if you need to be on the school run for younger siblings).
My Yr7 DC4 is often home an hour before I am - he's fine. He has to text to say he's home and alive. Some mornings I leave before he and DC3 do and again, that's fine - I ring 2 minutes before "leave the house now" time and nag them from a distance.
My DC1 started high school and straight away was in the house for 30 mins in a morning after I left to drop her sister at the childminder. And she would get in about an hour before my DH or I would get home.
She's sensible. And antisocial. So it's been no problem. In fact, when her Dad's hours changed recently and he started coming home earlier, she complained that it was cutting into her 'me' time. Bless
Depends on the child, but most 11 year olds are capable of letting themselves into the house after school and looking after themselves for an hour. I'm not sure I'd trust mine to get themselves out the house in time in the morning and lock up though.
DD is in yr 7 & 12 years old - she's perfectly happy to be left alone in the house in general. So for example, I'm self employed - I'll go off to work at 8am tomorrow, and she'll get up late, get dressed/have a leisurely breakfast, and then cycle over to meet me where I work in time for tea around 11.30 ish.
She also has keys & has come home and let herself in since end yr 5 or so (with me or DH arriving home around the same time but not feeling we have to be there on the dot).
But it is worth bearing in mind that the transition to secondary can be quite stressful - I think that for the first couple of weeks if you are able to be home for them when they get in it is really nice. (Obviously, not everyone can be!)
Of course an 11yr old can be left in the house for a short time, as long as they have no SN (always have to say that on MN) and have been " trained" !
Start training them now. Talk about what to do/not to do when they are in alone. eg don't open the door or answer the phone as long as the don't play with matches or stick stuff in plug sockets which is from the school of the bleeding obvious!
Set them up with a mobile to have to hand and pop down the shops for 10 mins to start with. Increase time slowly so that both you and they are happy it'll be fine.
Talk lots about " what ifs" and that they can always call you to ask.
Have you "trained" him to get home on his own too? if not and it's sensible he should start walking home ( or even part way home) from primary now. THe evenings are light and all the year 6 will be doing the same!