Do you know how to get kids clay that doesn't dry off of a wooden wall
Spray the surface to be cleaned with WD-40 and wipe clean with a soft cloth. If any stain remains, saturate a cotton ball with rubbing alcohol, blot the stain and rinse. Wipe any remaining residue with a damp sponge or cloth moistened with liquid dish soap.
I would use a plastic scraper to remove as much of the clay as possible. Then use mild soap and water to remove any residue.
I realize that the below is for removing clay from clothing but the same basic idea should apply.
Try using a plastic scraper to get it off.
Try dish liquid, a bit of baking soda and warm water to remove most of it.
If your kids appliied clay to the wall and its still wet, I would use a piece of fine wire holding it on either end, and slide it down the wall behind the clay to cut it off. Then use a metal scraper to get any leftover bits off.
You could try lemon essential oil--it's an all natural goo gone
Try sanding it off
A light sanding might do the trick with a high grade sanding paper.
Sanding is the best thing to do.
Hope this Helps! Jeremy - https://pahjodesigns.com