For me it was never enough, it was kinda like a bonus thing. A piece of the puzzle

Imagining is great but you need to get in the feeling of it, whatever your goal is. I did it through meditating and literally changing the things in my life that are blocking me from that which I seek.

also think abut these things:

Are you studying enough? are your techniques good? do you waste your time doing other things? etc. look at what you are doing and then improve it. LOA is not magic that gets you the grade you want without any work. Sure you can do whatever you want but you have to align yourself with the things you want.

Meditate and study(both LOA and the subject in your school)

imagining is good because it makes you feel good and happy, but if all we needed to do was imagine I think a lot people would live the life of their dreams or their nightmares.

Stop imagining if you're not doing the proper groundwork and start over. You might just end up suffering from Maladaptive daydreaming instead of passing your exams :)