Maths:
Regular and Irregular Polygons
https://www.bbc.co.uk/bitesize/articles/zgmcf82
English:
Reading and Using Texts
https://www.bbc.co.uk/bitesize/articles/zjbsm39
Music:
Structure and Texture
https://www.bbc.co.uk/bitesize/articles/zrj4ydm