Ilovecheese is right, No Outsiders isn't teaching children they're in the wrong body. It's age appropriate, fits with the laws and mainstream social beliefs in our country and doesn't in truth challenge any ordinary folks.
there's no suggestion teachers will tell children their mummy and daddy are wrong as Gonegirl fears. Most primary school teachers are skilled at negotiating the different cultures, lifestyles and belief systems their children present.
The only fear I have is that some Muslim/evangelical/orthodox parents will use this issue as an excuse to take their children out of mainstream. They're the very children who need to be exposed to more than rigid belief systems that say eg, if your'e gay, you'll burn in hell.