Shocking front page new!!!

I just happened to take a look at the Daily Mail front page today. (It is my preferred newspaper).
"English is a second language for 1 in 7 pupils" ..... That is the headline. However it is the first sentence of the story that jumped out at me.
" One in seven primary school pupils does not speak English as a first language"
It occurred to me that the sentence is grammatically incorrect. Surely this should read: -
" One in seven primary school pupils do not speak English as a first language."
It is no surprise to me that the subject is highlighted when clearly the author of this article has made a grammatical fau'par. (Double plural?!)
Perhaps the error was deliberate, given the subject matter. Well I'm sure the Daily Mail editor would use that as an excuse. Come on Mr Darce, I'm sure you don't expect us to fall for that one! Lets face it, you are not "The Sun" or the "The Star". Despite arguably strong political view, this newspaper is aimed at a more intellectual audience.

P.S. Please excuse any grammatical errors of my own. I only got a secondary school education. LOL