I'd be furious if I were you! This is exactly what they should be teaching - the skills he needs to succeed in school. Did you sign the IEP at the end of the meeting? You don't have to sign a plan you don't agree to. Did you notice their 1st 3 excuses contradict each other? He should already know these skills; other 5th graders don't know them; they can't teach them. If they can't teach them in elementary school, who will teach them in high school? Are you familiar with www.wrightslaw.com? A source for details on special ed laws, and how to work with schools.
Have you read Smart But Scattered? It offers specific suggestions about teaching executive functioning. A daily planner type folder that goes back and forth to school each day might help. Teacher writes (or checks that he has written) the day's homework assignments at the end of the day, Mom checks it, helps or oversees the homework, signs it, and kid returns it each day. That kind of organized, structured action each day might build some neural connections in the realm of planning and organization. At first, Mom and teacher are responsible for remembering to bring the folder back and forth - eventually, the child should take that responsibility. That was just an example - I don't know exactly what skill you want to teach or what problem you want to solve. Is he in Middle School next year? If he is changing classes and teachers, he will especially need a system to keep things straight.
I think what I would do in your place is come up with the specific accommodations you want to implement, to try out the last few weeks of this year. You could either meet with the teacher, or call another IEP meeting (they have to have the meeting if you ask, but if your school year is almost over, they could push it till next year if they are uncooperative - sounds like they might be). If you could just meet with the teacher with a "let's try this" kind of tone, you may get a quicker, friendlier response. If you get a plan going that works, a mini-trial for next year, no one should object to adding it into the IEP. Be sure to document every contact with the school in writing - this could become important if it all becomes a battle.
Consider taking an educational advocate with you to any IEP meeting- a friend who is IEP experienced (a teacher friend perhaps?) or even hiring a pro (look online in your area; it is an emerging profession, hasn't reached every area yet). My city school district used to train volunteers to come to IEPs as family advocates, but no more budget for that program. In any case, you are allowed to bring anyone you want to an IEP. Even if it is only a friend who can take notes, it helps to have back-up.