On the subject of raising children, Ali ibn Abi Taalib, radhiAllahu anhu advised:
“Play with them for the first seven years (of their life); then teach them for the next seven years; then advise them for the next seven years (and after that).”
*First Seven Years
In the first seven years, your goal is to build a strong connection to your child. This is the foundation, the base from which your relationship with them grows. If this is rock solid, the remaining years will be much easier. If this foundation forms poorly, the next years will be more challenging.
If you have young children, this (first seven years) is the time to roll up your sleeves and invest, heavily, in your and their future. In fact, you will be rewarded for all the righteous progeny that survives you, not just children, until the Day of Judgement.
*Next Seven Years
Once children reach seven, they are ready to learn. (Perhaps this is why Finland starts school at age seven.) This is the time they are sponges, ready to soak up anything and everything you tell them, teach them, show them, and do in front of them. If you built that solid foundation in ages 0-7, they are now more than willing and happy to learn from you.
This is the time to teach them everything — aqeedah, halaal and haraam, fiqh, all the things they need to know to survive throughout their life. Qur’an and seerah are also very important; as one prominent tabi’een said, “we learned seerah (frequently and in details) from our parents the way we learned Qur’an.”
Teach them sports, too; Rasulullah (salallahu alayhi wa sallam) said: “Teach your children swimming, archery and horseback riding.” They gain many benefits from it, including physical fitness, learning teamwork, and sportsmanship.
*The Final Seven Years
Once your children hit 14, they are probably already mukallaf (full adults Islamically, and accountable for their actions) — this happens at puberty, or at age 15 at the latest.
At this age (grade 8-9), you are mostly out of the picture. Children achieve independence; their personalities manifest; they look more to their peers than their parents and families. During these critical years, befriend them, advise them, and do what you can; understand that they are now full adults, and the choices are theirs to make, right or wrong.
If you worked hard during the last two periods of seven years, you will already be that trusted confidant, that advisor, that go-to person when they need help or advice. Be part of their lives, and advise them as best you can.