Christine Pessemier has written a great article about 10 ways to set up Orthodox children for moral failure. I agree with all 10 of these, but I would add one more: Public school your children. I know homeschooling is not for everyone, but if it is at all a possibility, you should try.
80% of kids from religious homes will abandon their faith after graduating from high school. And why shouldn’t they? Even if you have the “good school” in your district (Pro-tip: Everyone thinks they have the good school), the method of modern schooling is a sure recipe to weaken the family unit. Think about it: From the time they start school, they spend 8-12 waking hours of every day in the company of adults who are doing their best not to talk about Christianity so as not to offend, oppose school policy, or violate anyone’s rights. And that’s the good teachers. Before you assume that I am anti-teacher, I will clarify. There are plenty of teachers trying to work within what they will tell you is an incredibly flawed system, uphill, against the odds. Christian teachers ought to teach in the schools, if for no other reason than to provide light in the darkness. Then you have the teachers who actively seek to apostatize Christian kids. You remember one or two of those, just from your own school experience, right?
Mix all that together in an environment where their peers are elevated to the level of social importance that the parents should have and ignore the importance of the fact that few if any of the other students come from a family structure that is Christian. Most adults have a hard enough time struggling with this setup in the workplace, but we are talking about impressionable children who are getting a steady diet of this conditioning from Square One. As a reasonable adult, you can’t expect your children to escape unscathed from such a scenario. If you are reading this and have no kids yet, great. You have the time to plan your life in such a way that homeschooling is a possibility. If your kids are already in school and you are able, pull them out. We re-structured our entire lives when our eldest was in fourth grade because we were convicted of the importance of homeschooling. If you can’t homeschool (and not everyone can), you will do wonders toward making your kids one of the 20% who retain their faith upon graduating if you acknowledge that the school is a battleground for your kid’s soul. Actively assume that your kids are being taught things that you would not approve. Pray out loud with them at the beginning of every day for protection from their angels and saints, even if it’s just a quick one before they leave the car. Have age-appropriate discussions about the things we see in schools: sex ed being taught to kindergartners, transgender kids not knowing which bathroom to use, God being in no way responsible for the creation of the universe in science class, being allowed to defend others against bullies. I could keep going, but you catch my drift.
I would also make an exception for an excellent Orthodox school. Unfortunately, not everyone can afford private school tuition and finding a school near you might be a challenge, but if you can, building an Orthodox peer group for your kids in the shelter of an Orthodox curriculum is excellent. It still doesn’t strengthen family bonds in the way that homeschooling will, but all educational choices are a give and take.
We are called upon to be a people set apart. We are known by the fruit we bear, and as a parent, that fruit is your children. If your kids look and act like the culture, it’s time to step back and ask why.
Contumacia 
Wow. That last sentence is powerful.