In a Nutshell

Why don't they know their irregular verbs?  Why do they always drop the -s on third person singular verbs?  Why do they confuse "his" and "her"? Why do they never use the vocabulary that they regurgitated for a test? 

So many teachers put the blame on their students.  "They don't study."  "They don't work."  After all, all they have to do is learn the vocabulary and learn the grammar rules, and they will be fluent, right? 

Yet, I've seen students who worked very hard with little reward.  The first year I taught in a lycée I had two girls who memorized the entire page and a half of text for a test.  That they failed.  They could recite any part of the text, but they didn't understand it, so they had been unable to answer my questions. As Michael Jordan said, "You can practice shooting eight hours a day, but if your technique is wrong, all you will become is very good at shooting wrong."

Stephen Krashen's theory of comprehensible input is the only explanation I've ever found for so many students' lack of success.  

Krashen says, "Direct or explicit instruction is hypothesized to result in conscious learning, not subconscious acquisition.  If this hypothesis is correct, language acquisition theory predicts that the effect of explicit instruction will appear only when three conditions for the use of conscious learning (Monitor use) are met.  When the second language performer (1) consciously knows the rule, (2) has time to think about the rule, and (3) is focused on form.  So far, research results are consistent with these three predictions for grammar instruction." (Krashen, 1982, 2003)

Even if conscientious students have understood and learned the rule, conditions 2 and 3 are not met in a situation of oral communication.  There's no time to think and the focus is on meaning rather than form. And, as so many students will tell you, since they did not grasp what the other person said, they don't know which rule they need to use, even if it happens to be one that they have learned.  

Basically, this means that time spent on explicit grammar instruction is better used by furnishing quality input to our students in order to allow for subconscious acquisition.  We focus on meaning; we make it both compelling and comprehensible. Students are engaged and when they realize that they understand without thinking about it, lights go on in their eyes.  They feel successful and want more.  This is instrinsic motivation and the best classroom management tool there is.