Dear Alice, I heard this from my sex ed teacher in high school, and I was wondering if he was correct. He said that if there are cuts inside her mouth, the sperm can get into the bloodstream and possibly get the girl pregnant. With the exception of egg implantation, pregnancy can occur only when sperm make their way to eggs via the vagina. This is also the case when women are artificially inseminated.
Teachers know a lot, but sometimes they are wrong.
Glad you went searching for the truth that you can now present to your sex ed teacher by first clarifying what he said, and then respectfully making the correction, if it's necessary.