@danirabbit I'm cishet male and work in an after school program with grades ranging from Kinder to 5th. Until recently, if a kid tried to insult me by calling me "missus" or misgendering me, I would simply ignore the insult to show it doesn't phase me. I'm pretty confident in my gender identity and that stuff really doesn't bother me.
But I have come to learn that young children don't necessarily know what they say or why they say it, and the better option is to actually take those moments head on as a lesson instead of ignoring them. So now I'm deliberately to replying with something like "my pronouns are he/him please respect that". It's not for me- it's for the child who needs to learn that insults based on gender or sexuality really just aren't chill; it's for their peers who may need to see somebody model self-advocacy so they can do it too.