Writing about childhood boundaries

Shel Silverstein started the poem Where the Sidewalk Ends with:

And before the street begins,
And there the grass grows soft and white,
And there the sun burns crimson bright,
And there the moon-bird rests from his flight
To cool in the peppermint wind.

Write a story in which a sidewalk marks the boundary of where your children characters are allowed to go in their neighbourhood and about what happens when they cross it.