Students and staff at Ralston’s middle school and high schools in suburban Omaha are now required to wear masks following new cases of COVID-19 in the district. Ralston Public Schools announced the change Sunday, saying the policy applies to staff members and students from seventh- through 12th grades. Masking will be required through Sept. 16, when district officials will review the policy. Masks will be available at the schools for students who do not have one. Superintendent Mark Adler says the decision was made after three cases were identified in one classroom at the secondary level. The Ralston district was already requiring students, staff and visitors in preschool through sixth grade to wear masks.