Raising kids in a secular world - where do you draw the line?

We're trying to raise our kids with Christian values but they're constantly exposed to stuff at school and online that goes against what we believe. Not talking about anything extreme but just different worldviews. We don't want to be super restrictive or sheltering them, but we also want them to have a strong foundation. How do you guys handle conversations about worldly values vs biblical values without being preachy? My 10 year old is already asking tough questions and I want to engage with him thoughtfully instead of just saying no.