The paragraph that would help build tension if added to the story is:
As she struggled to free herself, the bus pulled into view. She waved her arms wildly, but the driver didn’t notice her. And she was still stuck. What was she going to do? She could not be late to school today.
This choice heightens the sense of urgency and frustration Sylvia feels as she struggles against the fence while the bus—her only means of getting to school on time—is within sight but not stopping for her.