Even if you join any academy ,they will only guide you a bit and they will just give an introduction of every topic. At the end it's you who will have to study to pass exams. And this thing has been said by academy teachers lots of time that it's you who will be studying they will just give you an idea about the subject.
Guidance that they provide ,you can get by scrolling different threads of tips and experience sharing section of this forum. Other than this I will recommend watching different video lectures available online. There are lectures on every single topic that are available online free of cost. And believe me these lectures are better than what you learn at academy. I don't think you really need to join any academy. But maybe keep in touch with the ones who are preparing for exams ,and maybe with some persons who have passed exams etc. You can get this type of guidance from video lectures or from this forum too. At the end it's upto you. But I don't think that acacademies can provide you that level of guidance that you need as compared to that of huge amounts of money that they take. Maybe join any individual teacher for different subjects. But for that too you will have to make sure that the teacher is competent or not. Or even if after all these things you want to join academy then at first check them by taking one optional subject or maybe one compulsory subject,then you will be able to know that how much help they provide in exam preparation. If you are satisfied then maybe take their whole course.
Regards.

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''Sufficient for us is Allah , and He is the best Disposer of affairs" Al-Quran