When they conflict, what should receive first priority in the classroom?

[MarkD]

In terms of your two-option poll, the obvious answer is option 1.
But your poll/question does not acknowledge that facts/the truth are not always obvious; they don't always leap off the page. Somebody has to define what the truth is, when facts are not clear and obvious, but are disputable. The institution that should settle such disputes should be the legislative branch of government - either the state legislature or the local school district board of education. Not individual parents.