Sprayed-on or trowelled-on surface material on wall and ceiling surfaces of some schools may be composed of asbestos-containing materials.  If the surface material is firmly attached, has a hard surface, and has no water damage, it should not be hazardous.  If the surface can produce powder or dust by hand pressure, it is advisable to seek professional advice before deciding what further course of action to take. Acoustical tiles, drop ceiling panels, joint compounds and even textured paint can sometimes contain asbestos.