* State regulations: Each state (in the US) and country has its own licensing regulations that specify minimum teacher-child ratios. These ratios often apply throughout the day, including nap time.
* Preschool's policies: Individual preschools may choose to have a more favorable ratio during nap time, even if it's not required by law, to ensure better supervision.
* Age of children: Younger children (e.g., toddlers) often have a lower teacher-child ratio than older preschoolers. This would apply to naptime as well.
* Number of children sleeping: If a significant portion of the class isn't napping, the teacher may be able to supervise the remaining sleepers with adequate support.
To find the specific naptime ratio for a particular preschool, you must check the preschool's license and its policies directly. Contact the preschool administrator or review their licensing information.