Explicit teaching of grammar with rules and gap-fill exercises out of context is an old tradition in Europe, although masses of research has tried to make it obsolete:
The reason is simple:
Today’s teachers teach the way they were taught by teachers who taught the way they were taught by… Ad infinitum.
It takes awareness, conscious study and practise to change fossilised methods. The first person, who made me aware of this approach to grammar, was Stephen Krashen with his Natural Approach:
The Swedish Curriculum for English is based on the same view:
Grammar still matters, especially in writing.
There are many ways students can learn language correctness more efficiently than with grammar books and grammar exercises. One of the basic principles of teaching grammar is mentioned in the revised commentary to the Swedish Curriculum for English:
Grammar should be taught when it is needed, not in case it is needed.
If there is interest among my followers, I could plan a web-based course with this and other principles and practices of learning language correctness to help you start on this track. Let me know.