Hiii..
There is no need to join any coaching for preparing, online course is the best course.
There is nothing like (good) free online coaching in India as of now..

Btw Online coaching is a great idea! . We can save time and efforts of going coaching classes when the sun is exactly on top of your head.

So, I cannot suggest you free websites because (there are none) but can suggest you free apps.

Khan Academy : The app is free, absolutely free. Also have good content. They provide content for almost every competitive exam. You dont have to pay them. But if youre interested you can donate money to them.
askIITians: This app is also free, recently launched but contain good stuff. The app targets JEE, NEET and SAT only. Because they have focused on only few exams thats the reason why they are really good. The teachers are ex-IITians so you can get good exposure. And they didnt even ask for any donation too.
Hope you get it...
For more queries please comment me on the comment section..
Good luck

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