Nowadays it is very common that teachers want that their students improve their English skills and they do it by teaching another subject in English. Doing this they increase the amount of time devoted to the English language.

There are different MATHS, SCIENCE, GEOGRAPHY AND ART pages, look at the top.

http://www.bbc.co.uk/schools/websites/4_11/ ( This page offers activities related to different subjects for primary students and higher)