Hello, this depends on you, my advice is that if you are preparing for a competition, then dummy schooling will be better for you. because a lot of time is lost in coming and going to school, like about 7 to 8 hours and just studying for school will not work. despite this you have to go to coaching, now you have limited time like about 3 to 4 hours, in that time you have to study for the board and also for competition.

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Hey,
Well going for dummy or schooling totally depends on how you are. If you are really very good with your basics i.e, even though you dont have extended knowledge regarding a particular topic, the knowledge you have is clear with an answer to each and every questions then it's ok.
As far as my vision is considered_
If you are among the top class bright students of your school with tremendous brain skills then you can easily copup with the school studies along with your coaching.Otherwise if you think that you are an average student and won't be able to manage your coaching along with school work then don't take risk & blindly go for a dummy school .
The purpose of joining a Good school is only that it will keep you connected socially in the world . Also it will improve your other Extra curricular activities like communication skills , presentation skills , personality transformation and much more.
But if you are an average student and dreaming for an IIT or another reputed college then blindly go forA Dummy School.

Hope it helps :)