Ive worked in childcare for decades and all kids do shitty things routinely. I would be confident in saying that all kids say sexist shit.
Often they're trying to understand gender when they're little and they say shit like "only girls can play T ball, baseball is for boys". Like they will invent and test out a theory of gender. All kids are gonna display sexism because it's a huge part of their lives. Even if their home is extremely feminist and/or queer, they're still going to school where most of the girls are still frequently wearing pink sparkly dresses with long hair and most of the boys have to have short hair and never can wear pink sparkly dresses. Even a drag show does not have the same level of exaggerated gender presentation as a preschool.
(This is very Western, btw. In other cultures, boys can wear pink, all boy toddlers have long hair, etc. Like Chinese immigrants seeing a baby in pink ask if its a girl or boy, Indian parents have their young sons wear long hair, etc).
Gender is very weird to kids and it is taught. A preschooler in one home came back with a note that they misidentified a short haired character as being a woman - as it the child had mistaken blue for red or B for D.
Kids are smart but they don't* have experience in emotional regulation, dont have much education or life experience, and at younger ages often are operating more at an instictual level. Humans are animals, and little kids do sometimes act kinda like, say, your cat might. Like, they just knock something down to see what will happen. They're not thinking about it. Once they start being able to answer "why?" the answer, "I don't know" is often genuine.
So yea, they ARE children.
So you handle it like you handle everything with children.
A. Prevention. Read kids a lot of feminist books conservatives want banned. Take opportunities to teach as they come up. Teach consent. Teach kids their rights. Teach them media literacy and critical thinking. Model mutual respect with kids. Foster trust so the kid can come to you or another safe adult for support. Model, model, model active feminism in your own life as they watch and imitate your behavior.
B. Respond to incidents systematically;
(1) Address the victim first. Make sure they're ok.
(2) Help the victim advocate for themselves.
"Bobby, I heard you tell Sarah that girls cant play with dinosaurs. Sarah, tell Bobby how that made you feel."
(3) Talk about it in a brief, honest, age appropriate way.
"All toys are for all kids. It's not ok to tell girls they cant play with the same toys."
(4) Help the child who did something wrong learn consequences and atonement
"Bobby, when you hurt someone's feelings, you can ask if they are ok, and how you can make it better. You can say sorry and ask Sarah to play, or if she wants space... OK, Sarah says she wants space from you. Sometimes when you are not nice to people, they don't want to play with you. If you are nice to her, she will play with you later."
"Because you were not being fair in sharing the dinosaurs, you can be done with them for today. You can try again tomorrow."
Dont be cruel, but be firm. Bobby is probably gonna tantrum about that. And that's ok. It's part of the process. Help him learn he has to calm his own body down, because the consequence will hold.
(5) You keep reinforcing it because kids, especially young kids, often make the same mistakes over and over.
(6) Use positive reinforcement. "Bobby, I saw you shared the dinosaurs with Sarah today. Im really proud of you."
(eta: it's normal and good to praise kids for doing stuff they "should be doing anyway", especially if it's a positive change. It helps!)
This of course goes for Sarah too, "Sarah I saw you told Bobby that all toys are for everyone. I am really proud of you for standing up for yourself."
Kids do indeed kill frogs.
I've had a kid, a toddler, straight up learn about death because she killed the class pet. Chucked it at a wall. Bawled her little eyes out. Probably traumatized about it.
Ive seen kids bite each other very badly and shit like that too.
Kids kill frogs. Kids do fucked up things. It can have serious consequences.
And you still have to respond to them as children because that is just simply how it works.
If a kid straight up commits murder I believe they should still be treated like a kid.
It's my belief that childhood is truly THE time of life to set kids up not just to succeed but to be decent to each other. They're a lot more open to it and you can truly give them a good start in life, or turn them around if they're in a bad place.
I have a lot more hope for the kids I see today because a lot of parents and teachers are really treating kids a lot better and teaching better lessons than when I was a kid. Wish they were inheriting a better world.