I enjoyed reading Johanna's message a lot. I found it very
interesting. Students' communicative proficiency has to be the goal
even before actual knowledge of English grammar.However explicit
reference to general grammar or syntactc rules  can be a short cut to
proficiency.Additionaly sometimes a teacher will have to tell the
students that a particular phrase is not following any grammar rules
because it is informal or colloquial...
Thank-you Juan