Children are often overlooked in feminism.  At one feminist message board I sometimes lurk at, with 3000+ members, there are occasionally threads about children’s issues, but these threads usually either get very little response, or if they get a response, it’s negative.  Some of the people at this message board (and other online feminist forums I’ve been a part of) are proudly anti-children, and claim that it’s feminist to be so; or, they argue that sexism in young children’s lives is irrelevant, or trivial to the point of not being worthy of discussion, because hey, they’re just kids.  I strongly disagree with this position.  Young children are highly impressionable, and they will be indoctrinated by patriarchy by default, if we make no attempt to change that.

One seemingly small example is how even very young children use “he” as the default pronoun, already understanding/learning, on some level, the subject/other dichotomy, where male = “normal” and female = “other.”

Most people don’t even notice that “he” is the default pronoun, nevermind attempt to change this, but for several years now, I’ve been making a concerted effort to say “she” more than “he,” mainly in my interactions with young children.  I was curious about the degree to which using the “he” pronoun is habit, how early it’s formed, and how easy/difficult it is to change/not form the habit.
Most commonly, this issue arises when there is an animal of unknown sex, either in media or real life.  For instance, we’ll see a squirrel on the lawn and someone says, “Oh, look!  What’s he doing?”

It took me several months, if not over a year, to say “she” habitually.  Over and over again, I’d say “he,” habitually, just like everyone else, then immediately correct myself by adding, “or she; I don’t know if that squirrel is a boy or a girl.”  Finally, I started saying “she” first instead of as an afterthought, at least sometimes… and now I’m at the point where I say “she” first an estimated 75% of the time.

Children’s reactions are fascinating!

Most children are startled, to varying degrees.  One day I met a little boy in the library, who seemed to be 3 or 4.  He was played with a stuffed caterpillar, and said something like, “Look at this caterpillar!”  I replied casually, “Oh, what’s she doing?”  He widened his eyes and exclaimed, “I think you’re right!  I think this caterpillar is a girl!”  I hadn’t directly made any proclamations about the caterpillar’s sex, I had merely referred to it with a female pronoun.  But rather than answer my question about the caterpillar, he latched on to my sadly-shocking use of “she.”
I had a similar experience while watching a squirrel with a 3-year-old girl.  We were sitting silent and still so as not to scare the animal, which was at the base of a tree a few feet away from us.  We were occasionally whispering about the squirrel’s activity, but when I made one comment that included the word “she” –  a comment so mundane I no longer remember it, like “Her tail is twitching” – the girl I was with loudly blurted out, “The squirrel has a vagina??” and the squirrel ran away!  I hadn’t been talking about the squirrel’s sex directly at all!

Other children get surprisingly upset with me for saying “she.”  Annoyed, almost angry.  When I’m out in nature with one particular 4-yr-old boy, and he points out a bird, and I say, e.g., “I wonder where she’s going,” he semi-snaps at me, “Maybe it’s a boy.  You don’t know!”  I reply with total calm, “Yup, maybe it’s a boy, maybe it’s a girl… we don’t know!”  I’m not trying to make children think that every animal we see is female, of course.  I’m merely trying to get them to think about the possibility that some of them are female.
Meanwhile, this 4-yr-old continues to call all animals “he” unless he knows for sure they’re female, and I’ve “compromised” by saying, “Wow, she ran up that tree so fast!  Or he!  Maybe it’s a boy!  We don’t know!”

Other children aren’t so startled by the word “she,” and even attempt to then use it themselves after hearing me use it, but aren’t so successful.  Once I was in the sandbox with a 3-year-old boy who was watching a toad, and called it “he.”  I called it “she,” not in a “That toad is a GIRL!” way, just in a casual way by using the pronoun “she” while talking about the toad.  The boy had no visible reaction, but called the toad “she” in his next sentence, as if he took it for granted that I knew the toad was female and was self-correcting.  But 2 or 3 sentences later, he had reverted back to “he,” also without really seeming to notice what he was doing.
Another time, I called a 2-yr-old girl’s caterpillar “her,” and the girl then referred to it with female pronouns once or twice, but couldn’t sustain it and brightly told me, “His name is Melissa!”

One time, I brought a 10-yr-old girl to the pet store so she could buy two pet mice.  The mice were separated by sex, females in one cage, males in another.  The girl knew she wanted two female mice and chose 2 feminine names for them, and was looking only at the mice in the female cage, yet she and the saleswoman both referred to ALL of the mice as “he” the entire time!  e.g. “Oh look at that one; he’s so active!  He’s stepping on his sister!”  It was pretty amazing to witness.

And here’s a quote from a 4-yr-old boy, while playing with a toy:

“When boys turn [this lever], it keeps turning like this, see?”
I asked, “What about when girls turn it?”
He said, “Yeah, when boys or girls turn it.”  Then he paused.  “When I said ‘boys,’ what I meant was ‘people.’”

And another exchange I had, with a 3-yr-old boy:

The boy asked me, in reference to a toy dinosaur, “Does he bite?”
I replied, looking thoughtfully at the dinosaur, “Hmm, I don’t know if she bites.”
He looked at me in surprise.  “Did you say ‘she’??”
“Yup,” I replied.  “Maybe that dinosaur is a girl!”
“No!” he said, laughing.
“Why not?”
“Because NO dinosaur is a girl!”

I’ve had numerous experiences like these over the years, in my interactions with hundreds of young children, and it’s become clear to me that “he” becomes the default VERY early in life, often by the age of 2 or 3.  More specifically, by the time a child is able to even say “he” and “she,” it is almost guaranteed that s/he uses “he” as the default.
I’ll add a disclaimer here saying that I haven’t done any formal studies/research about this and of course can’t make any definitive statements about all children everywhere.  But I’ve been working with young children for sixteen years, and this is what I have observed.

I am assuming this occurs because children hear the vast majority of adults using “he” as the default in everyday speech, and because “he” is the default in many children’s books/media.  But sexism in children’s books/media is a post for another time!