Are there any free textbooks/resources for high school physics online?

Hey @Asif Iqbal,

I am going to copy and paste @Sriram A 's answer as the formatting bugged out for him.

BBC Bitesize has very good sets of notes covering each topic, along with some questions.

Mathsmadeeasy and physicsandmathstutor are very good for brief notes, flashcards and past paper questions.

Isaacphysics and past paper olympiad questions are useful for developing problem solving skills.

The WJEC Physics specification is helpful for diagnosing areas for improvement.

Hope this helps!