I'm a teacher a primary headteacher, and can see a number of sides to this.
Firstly children do tell stories from their own point of view,its part of their development they are ego centric.
Sometimes they have a valid concern, sometimes they don't,sometimes it's a matter of opinion.
Teachers are not infallible, none of us are.
Sometimes parents appear not to know their kids and will blame the school for anything, I have kids and if someone says my ds2 was chatting in class, he probably was.
This, is combined with the bizarre complaints I have had over the years,often times these complaints ,will be screamed at a member of staff.
These non complaints (a lot of water bottle ,jumper ,homework issues)will often drown out more serious issues Which I do want to know about and will deal with.Its like a collective ' boy who cried wolf '.
Most parents (people)are reasonable as are most teachers, we all want the best for our children, we need to be supportive of each other,let the minor things go and deal with each other respectfully and kindly.