Six

I picked this up because it was on a list of fiction books with deaf characters, but it's also a middle-grade sci-fi which is right up my alley. So like most middle-grade sci-fi action stories, the adults are either not around or something happens to them, forcing the children to take action and be heroic! I wasn't necessarily struck by how realistic it was, but I liked the story well enough. I liked Michael, presumably black but possibly brown (only his dark skin was commented on) and a computer genius. Parker was an alright protagonist, nothing special.
My only real quibble was that the difference between American Sign Language and British Sign Language was shrugged off as comparable to the difference between American and British accents. Unless Emma had been studying ASL while in England, she wouldn't be able to land in America and be able to sign with the kids in her school immediately. They're really different languages.
Otherwise, anything else I didn't love was just aesthetic.