• SAT and JEE are two very different things. I'm going to stress on this again, Very different.
• JEE tests your concepts in PCM whereas SAT tests your critical thinking and also your English.
• If you clear JEE, you're certain to get an admission into an IIT, but there's no such guarantees when it comes to SAT. Because American universities also check your profile, your personality. So even after getting a perfect score in Sat, you're chances of getting an admit are zero if all you've done in life is study.
• SAT doesn't require as much preparation as JEE does, mostly because the reason I mentioned above, they also test your personality as a whole.

Hello friend, If you are from CBSE board then I will tell you that the syllabus will be same for both your board examinatons and JEE examinations as well.

You have to study consistently nd regularly.