The word "grammar" most certainly isn't the most favourite of students, not to mention the teachers. In fact, the most natural reaction upon encountering the word is to cringe!
Most teachers know the rules of grammar, I know. But it's one thing to know it and quite another to teach it effectively so that the students not only understand it , but are able to apply it in apt situations.
" My sister studies French"
and
" My sister is studying French" are not quite the same meaning. There is a subtle difference of time.