I would opt for testing. The thing that we have found is that having your facts in hand goes a long way toward stopping the school's stupid arguments. The more knowledge you have, the better advocate you'll be. Schools tend to have their standard bag of answers for parents that start "pushing" but if you can present the facts, often times they find themselves at a loss. My DS6' school has gotten to the point where they follow my lead because I have my facts. I don't make statements that can't be backed up by numbers and research. Now that your denial bubble has burst, it's time to educate yourself!

Good Luck and welcome!
Mom to DS 10, DS 11, DS 13
Ability doesn't make us, Choices do!