is there is any difference in school and coaching for iit jee exam. how coaching institute like allen kota organise the study periods.

Yes there's a major difference because school focuses on making you learn the concepts and write in the paper with proper explanation to get more and more marks whereas in such competitive exam you need have  your base absolutely clear about a subject rather than just memorising you need to understand it as well and there's also time management skills which you'll learn in coaching centers which will help you in exams
However doing coaching isn't that necessary you can study yourself just buy the study material of any such coaching and by making a schedule and studying regularly you'll be able to make it to the IITs