KS3
http://www.bbc.co.uk/education/subjects/zng4d2p
KS4
GCSE - Exam board Edexcel
Core
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/
Additional
http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/
Further additional
http://www.bbc.co.uk/schools/gcsebitesize/science/triple_edexcel/
General GCSE links:
FearofPhysics (good notes on many different Physics topics) gcsescience (Chemistry and Physics - site highly officially recommended by the government) Gondar Design Science (large site provided by a web design company)
BTEC Principals and Applications of Science http://qualifications.pearson.com/en/qualifications/btec-firsts/applied-science-2012-nqf.html
KS5 (A-Level)
Biology - AQA
http://www.aqa.org.uk/subjects/science/as-and-a-level/biology-2410
Chemistry - AQA
http://www.aqa.org.uk/subjects/science/as-and-a-level/chemistry-2420
Physics - Edexcel
http://qualifications.pearson.com/en/qualifications/edexcel-a-levels/physics-2008.html