It may well have asbestos in it. The stuff wound up in just about everything while it was in common use.
Seriously though, A few years back I was a licenced asbestos abatement contractor. My company line: if it’s older than 1980 have it tested. My practical line, the stuff isn’t as dangerous as some would have you believe. First it’s only dangerous if you inhale it. Second it’s very easy to manage.
Whether if not it has asbestos, celing texture can be nasty stuff (if it is the sparkly variety it could contain metalic glitter of chopped fiberglass) and the method of removal is the same. (With the exeption, asbestos should be disposed of as hazardous material.)
To tackle the job yourself you will need:
Several plastic garbage bags
A roll or masking tape
Some plastic film (disposable drop cloths work fine)
A garden sprayer
First remove everything from the room you dont want ruined, this will be messy. Or try your luck covering it with the dropcloths. Next seal off the room with the tape and plastic film, cover the floor as well taping the seams and around the baseboards.
Mist the ceiling lightly with the garden sprayer. Do not soak it, this could wet the plaster underneath and cause it to soften or cause staining that will leach through paint.
Put on long sleeves, goggles, respirator, gloves and boots. Tape your pant cuffs to your boots and tape the gloves to your sleeves.
Get up on the ladder and start scraping stopping only to let the blood back into your arms. After the lions share is off you may need to sand. A pole sander works well here.
Sweep the celing then the walls. Make a pile in the center of the room and bag it. Mist the celing and walls again and wipe. Roll up the plastic and bag it. Put your clothes directly into the wash.
Move on to next room.
Alternatively, you could pay someone like me who does crap like this for a living to do it.