Maths
5-a-day worksheets – https://corbettmaths.com/5-a-day/gcse/
Questions by grade & topic – https://www.mathsgenie.co.uk/gcse.html
Higher topic questions – https://justmaths.co.uk/2015/12/21/9-1-exam-questions-by-topic-higher-tier/
Foundation topic questions – https://justmaths.co.uk/2015/11/29/9-1-exam-questions-by-topic-foundation-version-2/

General websites
https://www.onmaths.com/
https://www.senecalearning.com/
https://corbettmaths.com/
https://vle.mathswatch.co.uk/vle/ (all students have their own logins and passwords)

Past papers
https://www.mathsgenie.co.uk/papers.html (with solutions!)
https://crashmaths.com/gcse-practice-papers/
https://revisionmaths.com/gcse-maths/gcse-maths-past-papers/edexcel-gcse-maths-past-papers

Youtube
Science and Maths by Primrose Kitten –https://www.youtube.com/channel/UCBgvmal8AR4QIK2e0EfJwaA
Hegartymaths- https://www.youtube.com/channel/UCLJnnnahpUYO2tOEcXe1mHA
Onmaths – https://www.youtube.com/watch?v=KPa9GanXqNE