Well, that's really a topic that needs a second thought
In my humble opinion I'd like to say that anytime you get involved in teaching any subject and in this case English you must never focus your lessons mostly on grammar, and exercises realization, why where is the communicative approach of your lesson? Remember that there've always been misconceptions at the time of conducting an English lesson, misconceptions which not every teacher has, that have mislead the very own process a good example of this it's the ways many teachers of English teach by having their students become familiar with communicative functions, grammar and exercises. And it's not about that It's about making them speak, which is the most important. Remember that the four basic skills to be developed in your students are speaking, listening, reading and writing, and the most important which doesnot exclude the others is speaking. Have you ever noticed the lack of knowledge somehow natives have on grammar?, they don't know most of the time why they use a lot of words such as prepositions, and the like, they just use them, 'cause they learned to speak not to how to use the grammar related.