In my experience, elementary teachers as a population do not do well with change. They struggle when new curricula are introduced, they get anxious when asked to do new class/school-wide assessments, even asking them to write their lesson plans in a new format throws them for a loop.
This thread began with the comment that your school had recently changed to IRLA as its reading leveling system. I would suspect that the teachers in your son's school are not completely comfortable with using the leveling system, and consequently can't explain how and why it is supposed to work, because they don't fully understand it themselves. Like many people who are insecure, but feel they have to present a front of authority, they may bluster or handwave through initial questions, and then backpedal or "reframe" (aka, lie) when confronted with inconsistencies.
Knowing that insecurity is probably playing a major role in the decision-making of the people involved, it may help to find ways to allow them to keep "face"(the illusion of competence and authority) while steering them toward appropriate placements and instruction for your child.
