Ideal Class Size - Opinions

On Linked In, in the Elementary Education group, there has been an ongoing discussion of what the ideal class size would be.  This question hasn't addressed, for the most part, funding or teacher quality, but simply the straightforward question, about IDEAL class size.  Interestingly, the answer seems to hover around 12 students.  As most people know, this number is between one-third and one-half of the currently common classroom sizes, which range from 20 to 36 students. 

My own comment was, "The best classes I have taught have had from 4 to 12 students.  What fun they are!  You can actually talk with the kids and enjoy the teachable moments.  You can treat each child as an individual and not just as members of a huge group."

The key for me is the teachable moment.  In a class of 24 or more, there is little opportunity to take advantage of the teachable moment.  Teachable moments are directly applicable to individual children.  Sometimes these teachable moments extend to quite a few individual children at a time, but the real focus is on getting individual children excited about their learning.  Children are quite different in what really excites them.  Novelty, of course, will excite many of them at a time, but true interest in something usually is much more specific.  With classes of 20 or more, this becomes a time and classroom management issue, especially when there are specific curricular goals to cover - and there almost always are specific learning goals mandated for the day.  

Intuitively, I think most classroom teachers know that small group instruction is better than large group.  That is why most classrooms I have subbed in have small reading groups for reading instruction.  Very rarely, is reading taught as whole group instruction.  A bit less frequently, but still often, math is also grouped.  And sometimes spelling lists are individualized or grouped.  But rarely does grouping extend to any other subject areas.  This is especially noticeable for science and social studies.  The most content-oriented (as opposed to skill-oriented) subjects are the least likely to be taught in small groups.  

What is so great about 12 students?  12 is enough to provide a lot of variety.  4 probably isn't - variety in terms of viewpoint, gender, personality, background, etc.  12 is a good number to provide interaction.  It is also a good number for dividing into even smaller groups, pairs, triads, quartets, and hexads.  12 means that talking is manageable.  12 children talking all at once isn't an aural assault.  A class of 24 or 36 is.  A class of 12 means that the teacher can talk to each child in a reasonable time, close to when they need it.  In a class of 12, you are dealing with individuals as often as you are dealing with a group.  There is time for the teacher to ask questions that will excite specific students, but not, perhaps, the whole group.  The teacher can ask a student about a project and go in depth, where this isn't possible with large groups.  The whole quality of the classroom changes.  

I think groups up to 20 can operate like this, but with groups larger than this, the instruction seems to change.  What do you think?