I think it"s very-very clever question... The classic English. I meant usual English. When americans correct mistakes in my notebook, I ask myself: What language do they speak? Do you understand?

I understood. Saying "Classic" I meant "Standart". But it's just formulation, which will not help to study language. I want to learn

Each national dialect(/set of dialects) has its own 'standard', 'prestige' form, so if you want to focus very specifically you must make a choice: you must choose a particular <em>national</em> Standard English, since there is no International Standard English.

If you say you want to study 'British English', people will generally understand that you mean the British 'standard' dialect. Likewise with 'American English'. I suggest you forget the word 'classic' here, and use 'standard' instead. 

What do you mean by "Classic English"? Are you talking about Early Modern English ie. the language Shakespeare used? Or are you asking about Old English ie. The language replaced by Middle English in the 13th century?