There is a vast difference in terms of experience and maturity between a 6 year old and a 12 year old for example. However, young adult and adult learners tend to share a certain level of maturity and exposure to the adult world.
Working in groups categorized by age has a number of disadvantages for all concerned in the language learning situation. There are of course two differing perspectives: those of the learner and the instructor.
Firstly, if we look at it from the perspective of a student with a low level of second language ability, working with peers that have a higher level of competency and therefore self-esteem will only diminish any confidence the ‘weaker’ learner may have. This in turn will lead to learner anxiety in all three recognized stages of language learning, (Input, Processing and Output; http://www.asian-efl-journal.com/thesis_M_Tanveer.pdf). Learner anxiety in turn will lead to low levels of motivation and eventually a mental ‘shut-down’ to the subject.
Conversely, if we look at the situation from a student who has a natural linguistic ability, having to work with someone that has a considerably lower level of language competence, leads to feelings of frustration and eventually resentment as they feel unchallenged in class. They may also experience a delay in their learning progress. Again these negative feelings toward the language class lead to a depletion in motivation levels.
On the opposite side of the learning experience is the instructor or teacher. Working with groups of learners based on their age rather than their ability presents a whole array of other problems in the classroom. Initially the teacher has the problem of choosing appropriate material. Do they teach to the lower level of the group of the higher? This in itself leads to yet another problem: how do I adapt the material to suit all levels of learner? The teacher is also expected to plan for the year ahead, but this proves impossible when flexibility is the key to teaching a class of mixed-ability. In the classroom managing a group, especially large groups, of mixed-ability students is complicated and it is very difficult to achieve lesson objectives. The instructor’s time is taken up trying to keep the stronger students challenged while giving the weaker students the extra support they require.
The advantages of working with learners in levels according to their language competence are numerous: firstly, both weaker and stronger language learners work at their own pace. The weaker students grow in confidence as they meet achievable language objectives, while the stronger students feel challenged with tasks that are aimed at their higher level of competence.
Secondly, the instructor benefits: it is clear what the learners should be capable of doing at their particular level, therefore choosing the correct material for the group is accomplishable; planning the course is easy; and designing lessons and achieving lesson objectives is doable.
The Council of Europe (www.coe.int/) encourages the use of working in levels according to competence in the language. The Common European Framework for Languages (CEFR:http://www.coe.int/t/DG4/Portfolio/?M=/main_pages/levels.html) has been designed with this in mind. Students are evaluated and placed in groups according to their level on the CEFR. These levels come with can-do statements designed to provide language teachers around the world with a set of level descriptors giving a clear list of competences in all areas of language skills. These standards are comparable on an international scale.