The Pennsylvania Department of Health notified the Norwin School District that a student had the highly contagious virus, prompting school officials to pull student immunization records.
They said 33 students hadn't had the vaccine and nine had registered for the prom. But a health department representative said Friday that the district had miscalculated the dates. The nine were contacted Friday morning and told they could attend prom after all.
But the students identified for exclusion still could have a problem with graduation, which falls within the eight- to 21-day after exposure that students are to be excluded from classes and activities.