It is always important to keep the lines of communication open. Sometimes kids will open up to a neighbor or a friends parent before they open up to their own. Kids tend to think their parents are “nuts” while their friend’s parents are cool and genius. That’s normal too.
Never be afraid to say “I love you” to your child. Even if they make fun or throw their hands up that their too old, they need to hear it and they need your hugs. They take it with them and tuck them into their heart. They pull it out and envelope themselves in it whenever they feel insecure or are on shakey footing.
Ask them about their day, ask them about their friends, don’t push just ask. Ask if they would like to invite their friends over or have a friend for Shabbos or dinner. Make sure you don’t JUDGE their friend, neither their appearance or their attitude. Especially if you don’t like their friend, ask if he would like to have that friend over again. You know the quote “keep your friends close and your enemies closer”. Get to know them, you will be surprised as to how much of an influence you can be on that child as well just by being polite and caring.
That doesn’t mean that you have to break your rules for anyone. You can say “if you don’t mind please wash up before dinner”, or “Avi would be happy to lend you a kippah if you didn’t come with one”. If they give you an argument don’t push it too far. Just ask politely if they would do it out of respect for you. If they say they would rather not, you can say “I won’t push it, but please consider it.”