Is it the schools responsibility to ensure the students' safety on their walk to school? If so, what is the regulation/code covering the school's responsibility?

Liability for student safety is a complex issue. How school districts
interpret their liability can vary. There is no federal law or code
that applies to all school districts.

Have you discussed your concern with the school or the school
district? A good contact would be the transportation director for the
school district. We would encourage you to talk with the school and the
school district to explore roles that schools, parents, and towns have to play to ensure children's safety as they walk to and from school.