Very timely for this topic... got a message today that
"the school conducted a practice Public Shelter Drill (used to be called Code Blue) and a practice Lockdown Drill (used to be called Code Red). In weeks ahead, the school will conduct practice Inclement Weather Drills."
Sadly the Code Red has been used a few times for real with the schools my girls attend, both in elementary years and as recently as last week when a shooting happened near their school and the gunman was on the run.

Code Red is a term used to describe an emergency/crisis at a School facility. Code Red alerts staff that imminent danger exists inside or outside the building and requires moving to an immediate lockdown mode. It requires all students to be accounted for and under supervision. During a Code Red no one, including parents, may enter the building. During a Code Red the telephone will not be answered.

Code Blue is a term used to alert staff that an emergency/crisis exist at or near a School facility. It requires all students to be accounted for and under supervision.