SOUTHBRIDGE, Worcester — Hundreds of white balloons fill the sky yesterday in honor of Kayla Osei-Opoku, a popular fourth-grader at West Street School who died Sunday when she was hit by a vehicle on West Main Street.

In celebration of the spirit of the 10-year-old girl, who had a reputation as the “smilingest” kid in school, Kayla’s classmates released the balloons into the air during a ceremony at the school’s upper field. Kayla’s identical-twin sister, Ayla, also a fourth-grader at West Street, attended the ceremony with her family. She was wearing a T-shirt with her sister’s picture on it and the inscription, “You Will Be Missed Kayla.”