I wouldn’t have a problem with groups of kids walking together to school. I walked along for at least 700m, about 8 or nine blocks, from my home to Jean Vanier school when I was young, but I think it’s too dangerous for kids to walk in the city these days.
At least the teens in this densely populated "lower-income" (American rating) city walk many blocks to middle and high school. Yet the ones with behavioral problems get shuttle service. Now let's talk about lack of attention span, and sense of purpose in life, and of Christian faith, and realize that walking alone is relatively not a real issue.
In HK our daughters walked down the hill, took public bus to Central MTR (Subway),then rode that 8 or 9 stops, and then another bus to school in the 4th grade.
But HK is a safe city.