Although it might help to know the difference between whose and who's

Anyway i don't think that explaining grammar points to 5 year olds in any language (including their mother tongue) is generally considered to be part of a successful teaching methodology to early learners. What having an explicit knowledge of English and ideally a good working knowledge of the first language of the students does allow a teacher to do is to anticipate the problems that students will have and tailor their lessons to accommodate for that. I'm sure Jake will be learning all about that during his TEFL certificate