Thank you for this explanat5ion.
I know that artificial conception, like artificial contraception, is a grave offense against the dignity of marriage (because it separates the sacred signs of lovemaking and life-making) and the dignity of the conceived child (because it treats him as a product/commodity, not a gift of the love embrace.)
However, I don't think artificial conception or contraception per se incur automatic excommunication. It's bad enough that they're mortal sins!
I believe you are right. In this instance the teacher knew and agreed to abide by Church teaching. She signed a contract. If she had qualms with the terms of the contract she should have declined to accept a position at the school.