I don't know if the Callan method works well or not, only that it is popular in Japan and involves a lot of drilling and repetition. We often have Japanese exchange students at my high school and their oral English is not very good. Some of these students , who take the Callan online lessons, take 20 or 40 one on one online lessons every month. It means they take one or two lessons every day. And they have audio files and text. They HAVE to buy them. They practise by themselves with these audio tapes. There are 12 stages in this method and ALL learners have to start from the 1st stage. Some of the Japanese teachers are impressed by the active lessons of the Callan teachers on the videos. I believe that maybe these lessons are better than some lessons in high schools or college, especially if students haven't had active speaking lessons taught in their school. I think speaking drills may work for beginners but it must be boring for advanced learners. Everyday lessons or everyday learning is the key to improving learning a language. It is difficult for the beginners to try to learn the language by themselves everyday. The students have to speak, have to repeat aloud when they take lessons in this Callan method, even if they are beginners. As you know it's very difficult to speak for beginners when they take lessons with native tutors. They often hesitate to speak in group lesson. The12 stages are very sound idea as students have motivation to climb up the ladder. Hopefully, those who complete the 1st stage of this method will go on to the next stage. This idea is good to keep up a learner's motivation to learn English.