The million dollar question for ESL teachers is often "Should I really teach that English concept at this level?"
Depending on what the concept is, the answer is frequently "No," even if the book you're using says otherwise. One thing we learn as we gain teaching experience is that sometimes some books show their authors' lack of intuition about the level at which something should be taught. It goes without saying that this problem is especially serious at the beginning levels. But what is an example of a concept introduced too early?
To illustrate, a serious stumbling block in the grammar/vocabulary/speaking book that we use at my school is the lesson on "present continuous with future meaning." This is such a common usage that some students simply pick it up without its being taught: "I'm going to the mall after school, teacher. I can't study for the test." However, nearly every time I teach it in the beginning level, in obedience to the curriculum based on the book, I regret it because my students are thrown into wailing, panicked confusion.
Why should this happen? It happens because at the point when the book introduces the above-mentioned usage of the present continuous, the students have just managed, through much effort, to learn the difference between, for example, "I'm working," meaning "now," and "I work," meaning "I work every day, I usually work," etc. They learn the distinction between the two tenses and sigh with relief that they've mastered something. But then their teacher, along with their book, starts to explain (in English, a language they don't really know yet) that "Sometimes instead of meaning "now," present continuous means "future."
"Oh," says a student, "like this, teacher? 'It is raining tomorrow'?" To which we must reply, "No, present continuous only has a future meaning with actions that are already planned." To which the students reply (or mutely think): "What means 'only'? What means 'actions'? What means 'already'?" "What means 'planned'?" True, some of them will catch on. Most, though, will think that they can't count on what they thought they had understood before. However, if we as teachers wait until the student proficiency is a bit higher--perhaps until the intermediate level--our explanation of this alternate usage of a verb tense will be understood much more quickly, without a hefty percentage of the class having their grammatical world turned upside down. Conversely, teaching it at the beginning level wastes precious class time and discourages many of the students.
To be clear, this is not a defense of coddling and underestimating students or of being afraid to challenge them. The bottom line, however, is that if a grammar point is sufficiently nuanced as to require considerable explanation, it should not be taught to beginners: using too much English to explain too hard English to students who know too little English quickly leads to the point of diminishing returns. Such students tend to learn less than they would if the teaching of the more abstract grammar points were postponed until they had acquired enough basic English to understand explanations of not-so-basic English.
