Well for what it's worth, I've found that there are two great age groups. Those in Grade 4 and below (aged on average 9.5 or less) and those in Grade 5 and above. The latter can be taught using many fun methods, including games, but are unable to focus upon or understand the more disciplined strategies that attack skills more intensively. In Grade 5 and above, I found the pupils are generally able to absorb all teaching strategies, including lesson types that had been designed with secondary students in mind. Not that I would suggest doing a lot of that sort of work -- compositions, language laboratory drills, etc.
Student or Learner