Clay for children needs to be soft enough for small hands, safe in the ways a classroom actually encounters, and either genuinely reusable or genuinely permanent. The choice is usually between a non-hardening modelling clay that can be used again and again and an air drying body that lets each child keep what they made.
Reusable or keepable, decided first
A non-hardening modelling clay is the cheaper long-run option for a class that models every week, because the same material comes back out of the tub. An air drying body costs more over a year and produces something a child takes home, which is often the point of the lesson. Deciding which of those the session is for settles the purchase faster than any product comparison.
Softness matters more than anything else
A stiff body defeats small hands and turns a modelling session into a wrestling match. Softer air drying bodies and the finer modelling clays work far better for younger children, and clay that has stiffened in storage can be softened by wrapping it with a damp cloth overnight rather than being written off.
The dust rule in a classroom
Wet clay is not the hazard. Dried clay sanded or swept releases respirable crystalline silica, and a classroom is precisely where dry scraps get brushed off tables at the end of a lesson. Wipe surfaces with a damp cloth rather than brushing them, keep scrap in a lidded bucket with water in it, and mop rather than sweep the floor. None of that costs anything and it is the whole of the practical advice.
Buying for a class rather than a project
Schools buying packets are paying craft prices for a bulk requirement. The pottery suppliers priced on this site sell air drying and modelling bodies by the bag, and the saving over a year is significant. Order enough that carriage is spread across several bags, and store the surplus sealed and cool, where it will keep indefinitely.
Questions people ask about childrens clay
What clay is safest for children?
Any wet clay is safe to handle. The precaution that matters is avoiding dry dust: wipe rather than brush surfaces, and keep scrap wet in a lidded bucket.
Should a class use air drying or reusable clay?
Reusable modelling clay costs less over a year; air drying clay lets each child keep their piece. Decide by what the lesson is for.
Can children's clay be fired?
Only if it is a genuine fireable body. Most classroom clay sold as air drying or modelling is not intended for a kiln and the packaging will say if it is.