And some of us do worse! Everybody overlooks the other statistic from this experiment: the girls' scores dropped as much as the boys rose, when playing the 'game'. I'd be more worried about that. Its not about reading, folks.
Anway, competition is normal in the working world (at least in America). So there's a problem regardless of school effects.
Sooner or later they need to work together anyway.
I'd rather suggest being honest about the fact that statistically speaking boys and girls are different and both have to respect each other.
Similar 'good' numbers for both, much worse 'bad' numbers for boys.