The Florida high school where a gunman killed 17 people in February opened on Wednesday for a new school year with three armed guards and other new security measures that some parents and students worried would not be enough.

Marjory Stoneman Douglas High School in Parkland, Florida, doubled its campus security detail to 18, including three armed uniformed sheriff's deputies. The school's 3,300 students wore new identification badges as they funneled through three entrances at the sprawling 45-acre campus.

During the school year, only one heavily monitored entrance will allow visitors on campus.