One day. Well, I say a day, but it was my afternoon lecture, so 2 hours or so. I was then given an assignment where I had to get into a group with three other students pick a disability (didn't matter which) and present it back to the class, so that they could learn about it.
19% of children in the UK (18% in the US) have some kind of disability or learning difficulty.
So when I hear other parents of children with special needs complain that teachers don't know what they're doing, or grumble that their child's difficulty wasn't recognised sooner, I feel angry for the parent, yet sad for the teacher. Qualified doctors sometimes fail to recognise disabilities and difficulties in children, so teachers stand no chance.
If your child has a teacher that does understand their needs and is able to accommodate them - be grateful. If you don't, don't feel as though you are passing your place by providing information that can help them to better understand your child's needs and your child. A good teacher wants to be able to reach and teach every child in their classroom.
You might not have a teaching qualification, but nobody knows your child like you.