One-on-One interactions will always be more effective than studying in groups.
Average classrooms consist of 30 students, and each class lasts about 45 minutes. If we divide 45 minutes by 30 students, that means that each student could be given 7.5 minutes per week (5 X 1.5) of time to SPEAK. Can we really expect anyone to learn anything in 7.5 minutes weekly?
One could argue that while the teacher is giving attention to one student the rest are at least passively participating, but when it comes to languages, if one student doesn't know one word, what happens to the the students who do? That's right, they lose interest!
One-on-one interactions in a world language for each student not only gives the teacher a break, it also significantly increases student motivation, and gives incredible results - please see the video testimonials from teachers who've incorporated this program in their world language classes.