I’ve used it with mixed success, it really does need dedicated time each day for it to be effective.
I had only two hours a week, which meant that the weekly programme took so much time to deliver as you had to spend time recapping the previous session.
When I had the luxury of teaching it on a daily basis it was far more successful and you could see the progress the students were making.
I like the content and the lesson plans, make it straightforward to teach.
It needs to be in a manageable group size – i’d say no more that between 10 and 12.
Hope this helps