It is an unfortunate truth that in a group learning class, many participants tend to learn less of the language being taught. This is due to lack of coordination, intellect, and sometimes motivation. For the people teaching a language, the list of problems include time allocation and the teaching process skills. It is important to assess not only the outcome but also the process. Alongside the group, the individual assessment must also be done.
For students, coordination can be a real pain. It takes a lot of energy and time for group work compared to individual work. Learning a new language in a group means coordinating schedules, arranging meets, and do the requisite correspondence. Decisions, when made, must be done collectively. The learning progress of every group member must be included. Task interdependence rears its head in this regard. Since language is best learned when members talk to each other, the students are actually dependent on one another. This remains true even if they do not share a common collaborative goal. Another source of the problem is the diversity of the group. Language learning becomes harder if there are cultural differences to cross. From another angle, this could be a boon as well.