I have been sent this link https://www.numerise.com/secondary-ready/
from Tor Bridge High which takes you to a free course called 'Secondary Ready' which has been designed to prepare Year 6 learners for joining school in Year 7 in September. The purpose of this course is to keep children mathematically fresh and is free of charge until September 2020.
This course can be accessed by all Year 6 pupils regardless of whether they are attending Tor Bridge High or not.
I hope you find it useful.