I actually was pretty sure that each of my kids had some issues before anyone else brought it to my attention. With my first son, I could tell that there was just something different about him. I knew that kids develop at different rates, but he just didn't seem to be hearing me a lot of the time, his words were kind of smooshed together, and he was constantly bouncing from one thing to the next. Transitions from one thing to the other would set him off into an unconsolable tantrum. I think I really knew for sure when I saw him with his classmates in Preschool. Honestly, I am still really annoyed that the preschool never said anything, because now I know he would have qualified for early intervention. Long story short, he is on the autism spectrum. He's turning 14 in a few weeks (How did that happen?!) He has been in special ed since K, and he's going to highschool next year. Suffice it to say, the special education he has recieved has been above and beyond amazing! The only really rotten thing that was said to me by a teacher was in second grade. She was a regular ed teacher and during an IEP meeting she said something along the lines of, "Oh,his poor wife someday. That's if he can ever get someone to marry him." Suffice it to say, I was horrified and so was his special ed teacher.
With my second son, we realized there was an issue in 2nd grade, when writing became a bigger part of his schooling. Suddenly he was crying before school and sad when he got home. The teachers and I came to the same conclusion at about the same time. Turns out he is gifted with a learning disability. I haven't really gotten a lot of negative comments about ds2.
We are in the process of getting my third son evaluated. I've suspected for the last few years that he has ADHD, but I wasn't sure if he was just hyper and incredibly distractable just at home or at school too. His teacher last year said that she thought he was just immature, and despite my doubts I decided to let it go another year. His teacher last year was amazing and hands on, but suffice it to say, her and ds3 were two peas in a pod! LOL! I figured that maybe with a more structured environment and teacher maybe he'd be more focused. Unfortunately, not so much! His issues are just more pronounced. I finally requested an eval, 3 days ago, and immediately got a message back from his teacher telling me she was planning on contacting me about the issues she has been seeing in the class. I wish she had contacted me earlier so that I wasn't going back and forth about what to do.
Honestly, some of the most hurtful things that have been said to me were things from family. With my first, it was denial that there were issues, until my older sister who I adore and is a special needs teacher, got a hold of them. With my second son it was the "He's so smart. He shouldn't be struggling in school. Maybe you just aren't being strict enough with him." With my third it is the, "Oh, it's just his age. He's fine, you just need to be tougher with him."
As for how I would want to be approached if I was unaware of the issues, I'd say always present the positives first. Then present the struggles you are seeing and ways that you think could help the child with those struggles. Basically, putting the most positive light on things, focusing on how special ed help could make things easier on the child, and lead to more success later on would be the way I'd want to be told. I think being prepared for the fact that some people may be defensive regardless of how you present it. So be compassionate.