The OP has said that she will go in to school to talk to the teacher about an area of the curriculum she is concerned with - in the first instance to find out a bit more about what they are teaching. She hasn't said she is marching in there and starting a campaign.
Even if they are not teaching literal creationism there is a difference between teaching:
"There is a god who created the universe and there are different stories that different cultures and religions tell to make sense of it, and here is one of them, let's use it to learn about god"
And
"different cultures and religions have different stories about how the universe came into being and here is one of them, let's use it to learn about religion"
It is reasonable for the OP to want to find out which one it is (and it may not be obvious from what her DC says). The first version is opinion presented as fact, the second version is factual.
I don't think it is about shielding her child from learning about religion, it is about knowing whether the school is working in the interests of the local community by teaching a fact-based RE curriculum, in a way that is sensitive to different cultures, or whether it is working in the interests of the church by using their captive audience for "Sunday school" type instruction.
Either way, she may not want to pull her child out, for other reasons, but it it is important to know whether in relation to RE she will be able to say to her child "your teacher is right, there are lots of different beliefs, isn't that interesting etc..." or "your teacher is lying when she tells you that there is definately a god who created the universe, that is just a belief of some people"
... If it is the second one the school is putting parents in a horrible and awkward position. That is not the OPs fault for being an uppity atheist, who can't be bothered to homeschool.