Student vaccinations are rarely a one-time-event anymore. With a tendency for immunities to wane, the CDC often recommends boosters.
This proves true with the meningitis vaccine.
In 2010, the CDC panel voted to recommend a booster for the meningococcal (MCV) shot. They contemplated simply moving the age back to 14 or 15, but didn’t want to leave kids unprotected for those few years.
So, the meningitis vaccine is now given at 11 or 12 and again a few years later before college, at about 18.
This short video from the National Center for Immunization and Respiratory Diseases (NCIRD) helps explain Meningococcal disease, why teenagers should try to steer clear of it, and how.