I would suggest a hidden camera to see who's really doing the mischief, since I don't believe in ghosts (though I realize the lack of fun in that answer).

Hopefully you can find some logical answer.

Otherwise, those that have formed this belief/experienced this will not be dissuaded. If you find no evidence, they'll say your expert wasn't correct, etc. No matter what you do, they are not going to be satisfied with the answer.

Course, maybe you need to find someone, unlike me, who does believe and ask for their suggestions...perhaps there's some way to 'cleanse' the area?

Tell it to go toward the light.

Hidden camera.

Jennifer Love Hewitt.

Oh yeah, workplace surveillance. That will be popular among the staff.

It's too early for me to come up with anything better (What would Harry Potter do?), but wow, what a premise for a ghost story.

If you make any kind of move on this, local media will be all over it.

Perhaps you could have a one-on-one chat with the union steward. You are probably lucky that no one has tipped off the news already, but if they do, you as management will be obliged to maintain that you are investigating these incidents as workplace pranks while the kitchen workers come off as idiots. I don't think anyone wants that.

This is almost a Lifetime movie in the making.

Or, KILL IT WITH FIRE!

Sorry, recently there was an Ask thread about a room with 'bad energy'. Don't know the outcome but maybe there are found within some helpful suggestions.

I love this story but am so glad I'm not dealing with it.

Maybe a good compromise is to find some way/excuse to do a rememeberance of the boy. Don't say what it's for. Those involved will know. The idea is that it will satisfy the spirit. And magically the poltergeist will be gone.

The boy? Well the staff is female and the apparition, or spirit, was seen to be a woman with ringlets in her hair, bright lipstick, and a 20's style dress.

I still do not know what I will do with this one. I will talk to the staff who have seen this. If it turns out to the the head custodian, well she is very good and level-headed and does well at her job. The cook, I don't know.

One idea is to put a few concealed cams up, without telling anyone at the school, but I would need to talk both the the union and to HR about that.

But the phenomena, for the most part, does not look like pranks, in that it's not like someone does something and then leaves for "it" to be found.

Mock me if you must, but I completely believe in an afterlife and I've had experiences. I wish I could "see dead people" but that is not my gift. Sounds as if she wants to make her prescense known; the staff could simply acknowledge her each day: yes, it sound silly, and I can hear some of you rolling your eyes at me, but someday you will see there really is life after this one.

Anyway, you could suggest to the staff that they greet "Mabel" when they come into the building in the morning; and they can nicely ask her to please stop leaving things lying around. She could just want respect, who knows? A friend of mine works at a nursing home; every morning coming in, she would trip on an unseen object. She found that if she says "Good morning" as she entered the building, she never tripped again.

Yeah, yeah, start your muttering now. I'm just sayin' it couldn't hurt. :^)

I find that fairly hard to take seriously. I agree that you should investigate it as you would any other reports of pranks/vandalism in the workplace caused by an unknown source. If (when) no video evidence turns up the nature of the discussion may change.

Hey, there's an app for that.
http://appshopper.com/entertainment/ghost-radar

Oh, and I would not advocate for concealed cameras. Just say "Huh, this is concerning - something seems to be going on, perhaps we have rats or there's a problem with the ventilation. Let's gather some video to see if we can see what's happening firsthand."

No downside - either things stop happening, or you end up being the guy with the entire world's first genuine video proof of paranormal activity.