It t is pretty standard to see older primary school kids Year 5 or 6 (so aged 10 or 11) walking to school unaccompanied and that to me presents more risks than leaving a sensible 10 year old at home for a short period.
The start of secondary school at 11 is a big stage of growing up (and a culture shock for many) and again it is totally standard for 11 year olds to make there own way to school by foot, bus, train, bike etc and many return home to an empty house before parents get back.
My daughter has been asking to walk to school by herself for much of the last year. She is very nearly 9 now. When I walk with her, she just cycles off ahead. She manages to cross the road by herself and is pretty good at looking around. The 4 year old is hopeless with roads.
There is always the odd moron who thinks it is reasonable to drive past the two schools near me at 50. Makes barely any sense as there is aways a queue on the morning at the end to get on the bigger main road. But still they are there risking playing schoolchild pinball on a morning. They are a way bigger risk than the potential child abductors.
Should really work out how to get 20 signs outside the schools for morning and evening. Some schools have got then in the area, but not ours. It really isn't going to make journeys longer as the queue at the end is inevitable in rush hour/school time. Not sure those that drive at 50 will be any more likely to obey a 20 as a 30.