From AZCentral:

… the board of Edu-Prize charter school in Gilbert decided to ban bicycles because of safety concerns.  …

Edu-Prize, a popular K-8 charter school, also requires signed parent waivers for students to be able to walk to school alone. The school has an enrollment of 1,263 with a waiting list of more than 1,000 students. It does not provide transportation.

The safety concerns that led to the policy change have included “one child weaving between cars” and children riding on sidewalks and putting pedestrians “in danger” because “the streets are not safe to ride on,” said Barbara Duncan, the school’s chief operating officer.

Children also have crossed major streets in “violation of our policy,” she said.

“All have put children at considerable risk, and our board has acted to keep children safe before there is a predictable event,” Duncan said in an e-mail. “The streets are marked with bike paths but are not wide enough for children or parents to safely use them.”

The school looks like this: