I would like to say that a good tennis academy is the one that really will improve your game.Each tennis pro has a different philosophy when comes to such subject.From my point of view i will sugest you to find a good enviroment Coach+Players+ITF Tournaments. It depends from each player on the financials (SPONSORS") capabilities.
A great success comes with a great eviroment as i did mention before.
And finally to give you a good example Andrea Gaudenzi & Thomas Muster+Coach (they did play and train toghether for a verry long time) wile traveling to ATP tournaments. And they had really good success:)
As a conclusion you can make your own environment...And thats the best academy you can find.
I so players who went in the states at prestigious tennis academies and they came out after 6 monts playng worst they went it.It all depends...