Being an efficient teacher is not at all the same thing as being an effective teacher. An efficient teacher might run a tight classroom with everything in its proper order. This teacher might organize seating charts, clearly display classroom rules, create detailed lesson plans and assignments, grade all class work in a timely fashion, attend all staff meetings, and fill out all the necessary reports. An efficient teacher may also communicate well with parents and administrators. In other words, an efficient teacher fulfills all of their responsibilities in a timely fashion and with great diligence.

This efficiency is an excellent thing, for it makes life easier for the teacher, students, parents, and administrators. But it does not necessarily mean that the teacher is effective. An effective teacher is one who truly helps their students learn and grow. An effective teacher presents material in a way students can understand and relate to. This teacher has a knack for taking difficult subject matter, breaking it down into manageable chunks, and delivering it in creative and interesting ways. This teacher tells stories and engages the students' imaginations. This teacher makes learning fun. This teacher recognizes students' strengths and weaknesses, meets them on their own levels, and engages their talents and interests. With an effective teacher, students really and truly learn, and they enjoy doing it.

You can be plenty efficient without being at all effetive.  Efficient teachers run smooth classrooms without wasted time.  They finish all their lessons, and return graded work in a timely manner.  None of that means the students are learning.  An effective teacher does all this, and gets results too.

Effectiveness has to do with what  happens in the front of the classroom, so to speak.  As has been well documented above, the effective teacher will ensure her students are learning and experiencing successes as they learn.  Efficiency is more of a personal attribute, it seems to me.  If I'm able to finish  tomorrow's reading and grading and preparing without taking up my entire evening, I'm efficient.  If I do all the "busy work" of teaching without spending hours each week, I'm efficient.  If I'm doing all my class work and paper work and extra duty work and I still have a little time to read and/or write on my own projects, I'm efficient.  Most of the time, I'm so not efficient.

Certainly everything that has been said is technically true.  It seems like efficient most often deals with timeliness and order - sense of organization.  Effectiveness is "did it work?"  So for a teacher, effective means, did the students get it?  Often, some of the most effective teachers are the most inefficient, disorganized, always getting interrupted by the bell mid-sentence, scatterbrained, but awesome, teachers.  The thing that makes them effective though, is usually charisma - which is a gift, not something you can necessarily develop through practice.

For the not-naturally-charismatic, I think there needs to be a balance.  I personally consider efficiency to be effective.  In this I mean that getting to the point (of anything, a lesson, a paper, directions) quickly and concisely is often the most effective.

Think about how many times you've tuned someone out because they seem to be talking and talking and talking and saying nothing.  Neither efficient, nor effective.  Case in point.

I can get the class started quickly, do my administrative tasks in a minimal amount of time, and be able to maintain good classroom order and be efficient.  That certainly doesn't mean that any one is learning anything, but it will look pretty.  That is not to say that an effective teacher can't be or shouldn't be efficient.  I get my administrative details like roll call, bulletin, etc. out of the way very quickly, so I have more time to teach, and while I tend to teach bell to bell, (efficient with time) I have had some success with students over the years.  So it's possible for the two concepts to coexist within the same instructor.

Effective teachers are able to get the students to learn what was intended. These teachers are capable of planning out lessons that will teach the students what the teachers wanted them to learn.

Efficient teachers act directly to produce an effect. When I think of teaching efficiently, I think of teachers who are able to teach lessons is an easy flowing and direct way, with little or no obstacles along the way.

I think that teachers who can be both effective and efficient have a wonderful gift. I also think that it takes time to master both.

If the question is intended to discuss the point from an educational standpoint, I will move the question to the education group.  I believe that there might not be an exact difference between an effective and efficient teacher.  In my mind, an effective teacher has to be efficient and an efficient one will probably be effective.  Teachers face a great deal of challenges.  One of these challenges is the ability to get the most out of a 40 minute teaching period.  The best of instructors can be rendered ineffective if time is not used efficiently.  For example, if class can be broken up into sections instead of one 40 minute layer, this is an effective and efficient use of time.  Teachers constantly battle this demon in terms of how to maximize time and ensure effective instruction.  In the final analysis, the question that has to be faced is how can time be used more efficiently in order to maximize effectiveness.  In this light, one can see that there is little difference between the effective and efficient teacher because both elements are needed in order to be a successful teacher.