Kids pretend to be stupider to avoid bullying...
... and this
is news? This is a surprising finding?
This isn't news, folks. It's the way it's been for a long, long time. I went through it, though I didn't hide anything; instead, I learned to be an arrogant, obnoxious SOB who showed off his intellect because it was the only thing he could do to hit back. I did know other kids who acted dumber than they were to keep from being a target.
Oh, and all your "anti-bullying" lectures and so on? They won't work, not much, not for long. What would work is changing the way that physical prowess and intellectual prowess are depicted on the most basic level, but that's not going to happen. The other thing that would work is actually approaching the problem rationally and by each instance on its own merits, but in general what happens is one-size-fits all, "zero tolerance" approaches that end up punishing the bullied parties along with the bullies... or actually punishing no one effectively.