Sheikh Muhammad Al-Hanooti, member of the North American Fiqh Council, states: “Before I go into details, I offer advice as a father, an educator and a person with some knowledge of Shari`ah.
A parent should try to make prayer and fasting attractive to a child. We should encourage a child to pray, as early as possible, and to start fasting when a child is able. Sometimes we ask a child to fast a part of the day in order to train him/her to fast in the future.
There is no need to tell the child that he/she is underage or of age because this will not help in making a child committed to prayer and fasting when he or she reaches the age of maturity.
The age of puberty for a boy is when he becomes sexually mature and when the girl starts menstruation.
It is very important to know that the time of puberty may not be enough for a boy or girl to be committed to observe prayer and fasting because they may not be mature enough for that commitment. Schools of Fiqh refer to this aspect. Allah Almighty says: “Prove orphans till they reach the marriageable age; then, if you find them of sound judgment, deliver over unto them their fortune…” (An-Nisa’: 6)
So, Allah combines puberty and capability to bear responsibility. The average of age according to these juristic studies is 15 years for both genders, which is the age of puberty and maturity.
I still say don’t look to the law as much as you look into the way you raise your children and discipline them.”