As long as you're not wearing a $5 nylon holster you should be ok. 

If we all knew the other's expectations.... which in this case is " what would the police like us to do about letting them know we are armed with a concealed weapon"...things would be less confusing..... it's why they involve students, teachers and Administrators in "Active Shooter and ALICE Drills"..... so they know what to do and not do.
My best guess is ...... it's something like ... " treat anyone with a weapon like a potential shooter/accessory; disarm them, cuff them, put them in the back of a car .............. we will sort it out later!!".................. which more likely than not will be hours not minutes. I can understand an live with that.......just don't want there to be any misunderstandings that get someone shot.
I remember the Sheriff in Fla.'s comment ; he stated his Deputy should have gone in and "killed the shooter".... not "engage"; "kill"..... I don't think any of us want to get caught in the middle of those rules of engagement.
Why aren't you dealing with the situation?
Amen, my brother.During my Narcotic undercover days I looked and dressed pretty rough. However I had a weapon and badge on sometimes. Twice I was "leveled down on" by other LEO that didn't know my identity. It is a scary feeling.
One time as I checked out a vehicle passenger side with a Remington 870 a backup officer arrived and only saw my long hair and a shotgun. He shouted drop the gun which I did immediately. Always regreted the pavement scratch on my shotgun but glad I didn't get shot.
All I can say is stay calm and do what the Officer says. He/she is in a very stressful sitution at the moment
I'm curious, every response that I've read here assumes a situation where the concealed carrier is holstered and just going out with the crowd. So, I have to ask, why are we carrying? I mean, in every one of the recent situations, there was only one shooter or if there were two, they weren't well coordinated. Why aren't you dealing with the situation?
I think from the OPs question and my responses ..... the shooting part is over.......I don't want to be standing around with a gun in my hand when I have "first contact" with responding police officers.....so if possible I'm going to transition back to 'Gray man" status ASAP.
So, carrying a Hi-Point and placing it in a students backpack before exiting would not be an option????
While there "may' be an other(s) "concealed weapon holder" present..... there "will" be police at some point. I think the OP was asking about that interaction and how to handle it........ without getting shot.
Keep your hands up, keep your hands away from anywhere near the gun for sure. Expect to end up at gunpoint (most likely on the ground), handcuffed, and staying that way until disarmed and your lawful status is confirmed. Depending on the level of chaos at the scene, this could be 5-60 minutes.