Secondary school uniform rules do baffle me sometimes. DS1 has to wear a tie, shirt, long trousers and blazer at all times even in the height of summer (though thankfully he can leave his jumper off...).
I work in a fully air conditioned office, with a formal dress code, due to the professional nature of our work. Despite this, we have official summer dress rules, which include ladies not having to wear tights(!), and men being able to dispense with ties and suit jackets.
It does seem a bit unfair that while we're allowed that, poor schoolchildren are sweating away in blazers and ties - all DSs friends at other schools have to wear theirs too, and none of the schools have aircon, so classrooms must be baking on a hot day.
I'm not sure any of them would wear shorts though, they'd rather be hot! well done to the boy concerned for making a stand. I was similarly quite irritating opinionated as a child, and because our uniform rules didnt say that our skirts or shirts had to be plain, just that they had to be a specific colour, I used to wear ones with patterns (stripes of different shades of the same colour for example). Teachers bloody hated me 
though they did change the uniform list the next year to state plain coloured in bold!