This study, by American/Canadian (one of each!) educational experts Cunningham and Stanovich, was written way back in 1998. It can be summed up by this line from it: "The more children read, the greater their vocabulary, reading comprehension and overall cognitive skills." Read on here www.aft.rg/sites/default/files/periodicals/cunningham.pdf.
This is an article from the Guardian Online in 2013 about how reading improves children's performance in all areas of the school curriculum https://www.theguardian.com/books/booksblog/2013/sep/16/reading-improves-childrens-brains.
This article from the Telegraph this summer suggests that we need to give more dedicated school time to reading www.telegraph.co.uk/education/2017/07/26/dedicated-reading-time-needs-heart-school-day/.
Now I'm not sure I agree with Dirk Foch's recommendation about the 'gamification' of testing methods but his statement that "good literacy skills remain the key building block of learning from which all other future success follows" exactly sums up my own thinking.
It is clear that people have been talking about these issues for years, but now we need to stop talking and start acting!