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 addition heightens the urgency and anxiety of Sylvia's situation, creating a sense of desperation as she tries to get the bus driver's attention while being physically stuck.