“The wheels on the bus go ’round and ’round, but that’s not the song that’s playing overhead — it’s “Twinkle, Twinkle, Little Star,” with a few key words changed: Twinkle, twinkle little star, what a wonderful child you are. With bright eyes and nice round cheeks. Intelligent person from head to feet. Driver Mary Petit pushes play on the CD just before pulling into a south-side apartment complex parking lot, where three sleepy toddlers and their caregivers climb aboard. Each kiddo grabs a Bye-Bye Bear from a bag up front — right near the posted Morning Message reminding parents they can handle this, they’re safe, keep breathing — and hands the well-worn stuffed animals to their families, who give the bears hugs and kisses before handing them back, saying their goodbyes and de-boarding. Petit’s been driving a school bus for 19 years, but she’s never had a route quite like this….”