I have not seen NAPLAN results ever,so really can't comment but if it's out of 6, highest being a band 6, then i think that the acceptable range should have been a 3.

Why base questions on stuff which they haven't learned yet though? Or were the kids meant to be taught the subject at school, but the teachers didn't get around to it??

Who knows what they teach in school these days... maye be that the muslims hate the jews and vice versa. I hope that was a question asked in the NAPLAN, if my son got taught that.