I have three grown children, and one of them happens to have been adopted in infancy after a "less-than-ideal" start. He had no problems whatsoever, and as part of the adoption follow-up (because of his rough beginnings) he had some testing and came out perfectly fine. When he got to kindergarten he began seeming stressed out and not able to do things (identify letters, numbers, etc.) that he did at home. The teacher started in with the whole "what's wrong with him" thing, and I had no reason to think there was the least little thing wrong with him (because I knew him, saw what he did and was like at home, and knew how he'd done on tests.
The teacher (and others at the school just thought I was an "un-objective mother"), so they wouldn't let up. They turned things into a whole big thing about "what's wrong with him" and "what kind of learning disability does he have" (even though he didn't show the usual signs of a learning disability at all). I knew I didn't have the answers to the mystery, but I also knew they were out-and-out wrong, based on the fact that they believed things about him that just were not true (based on what I, myself, knew and had witnessed). He is my first child, and I thought I should be "reasonable enough" to consider the possibility that I could be wrong and maybe they were right.
Regret: That I was too young and too unsure of myself to have just said to them (essentially) "Shut up. You clearly don't know what you're talking about, so leave him alone and leave me alone; and if you don't, his father and I will sue." They "did a job on him". He got so he wondered what was "wrong" with him too. The whole thing turned into a long-term problem that affected him throughout his school years. Now, I'm confident enough to know that I wasn't wrong to view these people as a bunch of mediocre morons who didn't know their bottoms from their elbows, let alone understand children and how to teach children. His father and I regret that we didn't pull him out of that obviously mediocre and poorly managed school a few weeks after the problem showed up. Interesting note: A neighbor had told them my son was adopted, and I can't help but suspect that they started zeroing in on him when they learned that (even though he'd been adopted as an infant and was a perfectly happy and normal little boy).
As I write this (and he's over 30 now) I still feel kind of nauseous to think of the job those unskilled, unintelligent, poor excuses for teachers and school officials did on this little kid.