how old is your daughter? i agree with the pps who said to talk to the teacher, but i also would suggest talking to your daughter.
when i was in elementary school (age 7 i think) a teacher told me that i could not be a doctor when i grew up because I was a girl. In front of the entire class.
i was so angry, but kept quiet and told my mom that night. My mom not only reassured me that I could be a doctor if i really wanted and if I worked hard, but she also told me about how some people haven't thought about or learned about different ideas, so they continue to live in their world with only their ideas. We talked about how sad it is not to at least consider another way of living and how much that teacher was missing out on. We also talked about picking your battles, so I didn't go back to school and tell the teacher that i could be a doctor if I wanted (the teacher had decided that I would be a nurse), but I did tell all my friends that i felt sad for the teacher because she hadn't heard that women could do any job that men could do!
Anyway, long story short, this may be a great time to talk to your daughter about manifestations of ignorance, and how how to start to deal with such things.
Oh, and way to go nursing your 18 month old