KS2 Bitesize - http://www.bbc.co.uk/bitesize/ks2/
A site with both Maths and English based quizzes which are marked as you go along - https://www.educationquizzes.com/ks2/maths/
Activities to reinforce and practise a range of spelling rules -
http://www.keystage2literacy.co.uk/spellings-menu.html
This site has loads of Maths games which help to practise a range of skills -
https://www.mathplayground.com/games.html
IXL have separate pages of skills linked to individual Year groups. The Y6 page has links to practise both English and Maths skills. Pages are then split into skills of which each has a practise question for the children to think about - https://uk.ixl.com/promo?partner=google&campaign=1187&adGroup=Key+Stage+2&gclid=CPPa8teS_8kCFQbnwgodgOIB6A