When I was barely seven, and we lived in Sydney's Upper North Shore, I used to walk home from school not just by myself but taking my year and a half younger sister with me.
The route I walked is only one kilometre long (I would have guessed it as more, it felt like a long way), but involved some reasonably hairy road crossings. Grosvenor Rd, where the school is, has terrible traffic, which made crossing to Ortona Rd too dangerous. There are traffic lights at the top, but going that way then required crossing Eton and Westbourne Rds where they meet the Pacific Highway, at wide, flared junctions into which 60km/hr (40mph) vehicles can turn without slowing much.
On the other hand, the streets in Sydney's North Shore are mostly (as you can see in the picture above) wide enough to have broad nature strips between the carriageway and the footpath, so walking along them is in some ways safer than walking along pavements in Oxford, where a slip could easily result in a fall onto the road.
That would be one of my concerns if Helen were walking by herself: the walk along Howard St seems pretty safe, with no side-roads or driveway entrances, but there's a fairly continuous stream of motor vehicles passing by, sometimes faster than the 20mph (32km/hr) speed limit, despite the raised tables, and a slip, perhaps while running or skipping, could be nasty. It's particularly bad on bin days.
The other concern would be crossing Boundary Brook twice, once at the north with fewer vehicles but potentially fast-moving ones, and once outside the school, with a mess of vehicles going every which way and poorly parked vehicles blocking sight lines.
There are no rules in the UK about letting children walk to school unaccompanied, but it seems many people would consider ten a reasonable age, and eight a stretch.
In the 70’s and 80’s it was the same in the UK, kids walked to school mostly without their parents, usually with friends or siblings. In fact it would have been pretty embarrassing to be walked to school by a parent in my school. I walked alone to school at least from the age of 7. No idea when this changed and taking kids to school became the norm.
I was walked to preschool and kindergarten. From 1st class, age 6, I walked without parental supervision, but never alone. Living in a cul de sac subdivision there was a constant stream of kids walking to and from school and no traffic. Families mostly only had 1 car, which was driven to work or the train station by fathers early in the morning, except for when the wife needed it for shopping. By 3rd class I was cycling to school on the roads since there weren't many footpaths on the kerbs (and they were full of pedestrians anyway). A friend of mine did end up in hospital with a broken an arm and dislocated shoulder when they were collected by a car at a corner. But that was the only injury commuting to infants or primary school.
My sister walked my niece to and from school every day till the end of primary school. Even though it was only 500m and there is an underpass under the main road. This was typical apparently. She was catching a bus to highschool, but now they have moved to where there isn't a bus, so she gets driven every day.
I was born in Berlin in August 1942 and so started school in 1948. My memories are very punctuated, mostly because I have a tendency to remember unhappy situations rather than happy ones, and have also therefore been reluctant to resurrect them.
Anyway: postwar Berlin at this stage was still full of ruined buildings and demobbed soldiers, both of which I had to negotiate on my walk to school unaccompanied by a parent, but at least in my second year in charge of taking my younger sister to her kindergarten on the way, and the little girl from upstairs to her infant class. I have no way of determining the distance now, but it did involve a reasonably long walk in my recollection, and a major traffic road, manned by a policeman. This was a cause of anxiety to me, as we were all given food for lunch in metal canisters we brought with us, and were under strict instructions to finish eating it all before heading off for home for the afternoon. A sensible measure to ensure that children were fed in impoverished and blockaded Berlin, rather than providing adults with the contents, but I loathed the food, being much more palatably fed at home, and so tended to leave the porridge substance in my canister. But was the policeman going to stop me and ask to look inside and find I hadn't complied with the rule? He never did of course.
An extraordinarily lucky encounter, in retrospect (unless there is a suppressed memory involved) was the nice man who asked me if I could please help him with something nearby, and being a nice child I of course agreed. He took me into one of the ruins and - as I recall - lifted my skirt, and then just let me go. I never told anyone.
What my mother was doing in all this is unclear. She wasn't working. Later, in Sydney, when she was in a job, there was no issue about my sister and me walking to and from school together, from the age of 8 in my case, and 5 in hers. Although apparently I attacked someone who was attacking her on the way to school in Bondi, in the very early days when we spoke virtually no English. The only bother for both of us later, in Neutral Bay, was avoiding the side of the road with barking dogs.
You did walk to school with Jenny and there were also quite a few other children on the way. You almost always walked with your nose in a book. A young, protective neighbor said he kept an eye on you both.