A formal language school can offer excellent interaction and feedback, but one word of caution is necessary.
Too many people think that simply attending language school will enable them to learn a language. In fact, whether you are attending formal classes or not, you will do most of your learning on your own.
You direct your own listening and reading activity. You work on learning and relearning words and phrases, you train yourself to pronounce correctly, and you work on your writing.
When you choose the activity that suits your mood, your studies are more intense than when you are forced to follow the teacher’s agenda. Learning a new language is most enjoyable when you are learning quickly, which requires intensity. In physical training you often hear the expression “no pain, no gain.”
Only intensely overworking certain muscles will bring about the increased strength and performance of those muscles. Casual exercise will not do more than maintain an existing level of fitness.
The same is true of language training. Your goal should be constant improvement towards fluency, not just maintenance.
You need to overwork the language processing capability of your brain by constant and frequent repetition during a period of intense learning. This period may vary from three months to twelve months depending on your starting point and your goals. During this period you must maintain a sustained commitment to your task. Fluency cannot be attained without sweat forming on your brow.
It can, and should, still be enjoyable, but just as in physical exercise, the methods of training must be efficient. In fact, the greater the efficiency of the training methods the more intense the learning experience, and therefore the better the results.