A question about teeth? what causes stains on the enamel in kids?

Depends.: Intrinsic stain (within the tooth) can be caused by high fever during tooth formation, meds taken during tooth formation or developmental problem (genetics). Extrinsic (surface stain) stain can be caused by foods, such as coffee, cola, grape juice etc combined with poor brushing habits.

A few things: Could be food intake, lack of hygiene, antibiotics, hx of sickness dureing tooth development. It depends on the type of stain and depth of stain. See your dentist for more.