My 9 yo's teacher has invented a new term "North Western Hemisphere"?

There is definitely no such thing as a "North Western Hemisphere," you are correct. It's impossible. This is a tricky situation for you, though. If you don't say anything, you are allowing your child to be taught something that is wrong. If you only say something to your child and not the teacher, you are teaching your kid that it's OK not to listen to his/her teachers. If you say something to the teacher, you could possibly create animosity between her and your child, and that wouldn't be good. Whatever you do, good luck. I understand why you are frustrated.

its not really a new term. There is a such thing as a north western hemisphere. lets say you take a globe and cut it three times.you should have eight pieces. the one eighth of the globe would be considered the north-western hemisphere. and if all honesty ask the teacher as well. He or she should be able to answer where He or she got that term from

No don't bother to correct her, just teach your child the truth. If she tests him on this, and he looses points, then get in her face, but until then, just do your best to monitor your child's correct education. It is what you should be doing anyways, and it seems like you are a good parent and doing that.

She needs to have her teaching license revoked and be ridden out of town of a rail. This kind of ignorance in the teaching profession is completely unacceptable.

if teaching that yes .though i think i've seen the same glitch . send a note .a detention note !

Absolutely correct her...explaining that hemi means half.