Testing is a different question from eligibility/placement/services. If the relationship is contentious, I could see it affecting the latter, but not necessarily the former. The issue isn't usually the testing data, but decisions about implementing recommendations issuing from the testing. Full disclosure: I'm usually on the other side of the table, so, naturally, in that role I believe in the validity of my own testing results...

...pronounced like the long vowel and first letter of the alphabet...