How long will your period last?
An average period should last between 2 to 8 days,and should occur every 20 to 35 days
I'm not sure why you specify children's period - children generally do not menstruate, it occurs from puberty into adulthood. Menstruation at any age can vary on the individual but typically menstruation will last 5-7 days. Younger people may experience longer periods or shorter periods due to hormonal imbalance during puberty.