Just wanted to touch on the combination of these two here
Utilization of the phone system/whatever other ability there is to provide the information for the full school is vital depending on the purpose of the lockdown. Especially in the case of the "crazy machete" type situation mentioned earlier: an internal issue needs to be communicated fully and as widely as possible with as much information given as clearly as possible for people to be able to make the best decisions they can.
Codenames are not a good system as there are too many variables at play where they fail: is every single individual in the school at that moment someone who has been provided information and training on the codename variants and their meanings? There are too many people who could be in the school for any number of legitimate reasons for that day alone that do not know the codename system for that school. Instead it is always better to provide as much information as possible and relevant/important to the situation in as clear and succinct a manner as possible. Is the lockdown due to an issue in the surrounding area that does not directly impact the school's ability to function outside of restricting outside access? Or is there something that is happening and teachers will need to move students from a specific portion of the building while others remain in place?
Any lockdown is going to be different from any other lockdown; creating a system that relies on fixed "If X do Y" creates issues immediately when something does not fit perfectly into those scenarios and causes people to have to process through their mental Rolodex of what they are supposed to do instead of hearing the information and responding accordingly.
Last piece to add on: does your system work when the office itself is unable to send the alert? Are the teacher's aware of what the process is for enacting the lockdown scenario? If you are using the phone system is it centralized to only a singular point being able to make the call to all handsets or is each handset able to do this? Have the teachers practiced making a call like that if they ever need to due to the incident originating in their class or area?
