Walking to School by Eve Bunting, illustrated by Michael Dooling

From chapters.ca:
Walking to school can be hard if you live in Belfast, Northern Ireland. It's downright dangerous if you're a Catholic, like Allison, and the shortest route to your school goes through a Protestant neighbourhood. But sometimes a ray of kindness cuts through the violence. That's what happens when a demonstrator rips a brass button off Allison's new school blazer, and a Protestant girl not only retrieves the button but returns it to Allison.