This was on the first day of class for this semester and I have been intrigued by it for awhile to see if it's true or not, I searched the sub and it looks like no one has really asked this question, so I decided to jump on it.
Thanks for the responses in advance! I love history so I hope I can get an answer for this, since it's been bugging me for a few weeks now.
EDIT: I should also add that the time she stated was 7000 bc or so if that helps your search.
In the bible, Joshua is said to have constructed some buildings wherein a first-born child, presumably the offspring of a slave, was killed and then placed under the foundation as a way to ward off evil. Your teacher is profoundly mistaken if she believes that this was even remotely common throughout ancient societies, however. I'm actually rather shocked that an educator would speak in general terms like that, if that is indeed what happened in your class. I would disregard what she said and consider correcting her.
Hi, you might consider x-posting to /r/AskAnthropology: there area few more anthropologists & archaeologists there who may have more knowledge on this question