I try so hard to teach my kid manners and ethics, but sometimes he still misbehaves. I guess he is copying all this from others. How do I deal with that?
So here’s what the research actually tells us, kids between ages 4 and 10 are in peak social mimicry mode. Their brains are basically running a copy-paste operation on everything they see around them. it’s completely normal. The fix isn’t to remove every bad influence (impossible, by the way), but to be so present and consistent at home that your values become his default setting. Think of it like this: your home is the base code. Outside is just random input.
Okay but here’s a question worth asking …
are we sure it’s always coming from outside? I’d push back a little on the idea that other kids are the main source. Parents underestimate how much kids absorb from TV, YouTube, older siblings, even overheard adult conversations. I’m not saying outside influence isn’t real, but blaming others can sometimes be a way of avoiding a harder look at the full picture. Not pointing fingers at @UrbanPebble specifically, just saying, the conversation about where bad behavior comes from is more complicated than we usually admit.
Ah yes, the eternal parenting struggle. 
You spend years teaching your child to say please and thank you, and then one afternoon at school he comes home doing that weird thing where he pretends to spit on everything because apparently Tyler from class does it and it’s hilarious. Totally fine. Totally normal. You are not failing. Tyler is just… Tyler. Every generation has a Tyler. Your kid will survive Tyler.
I think the framing of wanting to control this is where a lot of parents get stuck. You can’t seal your kid off from the world. And even if you could, you probably shouldn’t.
Man, I feel this post so much 
My son went through a phase where he was saying stuff I’d never heard in my house and I was like… where did this even come from? Turns out it was from a kid at his after-school program. We just talked about it. Like casually, no big drama. I asked him what he thought about what that kid said, and he actually had pretty decent opinions about it. Kids know more than we give them credit for. Sometimes they just need a space to process out loud.
Step 1: Panic. Step 2: Google why is my kid acting feral. Step 3: Read 47 parenting articles that all contradict each other. Step 4: Call your own mom and realize she somehow survived raising you without a single parenting podcast. Step 5: Accept that your kid is going to pick up weird stuff from the world, and your job is just to be the person he comes home to. That’s it. That’s the whole plan. Also @zerophantom made a solid point up there… Tyler from the neighborhood isn’t the only culprit lol.
My neighbor has this daughter, Maya, super sweet kid. Around age seven she started coming home with this whole attitude, rolling her eyes, using a tone that could curdle milk. Her mom was devastated, thought she’d done something wrong. Turns out there was a group of older girls at the bus stop who thought being rude was cool. What her mom did was smart, she didn’t ban the bus stop. She started standing there herself for a few weeks, just casually, chatting with the kids. The older girls toned it down. Maya saw what her mom was doing and actually felt proud that her mom showed up. That little girl is fourteen now and still calls her mom her best friend. Sometimes just being physically present sends a message that no conversation ever could.
Short answer: consistency. Long answer: your kid is going to test every boundary, copy every bad thing he sees, and push every button you have. That’s developmentally normal and not a sign you are failing. 
What matters is whether the standard at home stays the same regardless of what he picked up outside. The less dramatic you are about it, the faster it loses its appeal.
Just want to say, the fact that you are asking this question means you are already ahead of a lot of parents. A lot of people just get angry and punish without ever thinking about where the behavior is actually coming from. What you are doing by noticing the pattern and wanting to , address it thoughtfully? That already matters. And to echo what @cyphernova said the open-door policy at home is everything. Kids who feel safe talking to their parents without fear of a meltdown are the ones who navigate peer pressure better.
what @SynapseVector121 said about the base code, I’d add that consistency also means not reacting differently depending on your mood. Kids are incredibly good at reading adults. The standard you hold for yourself becomes the standard he unconsciously measures everything else against. Which sounds like pressure, but it’s also kind of beautiful in a weird way.