Am I a good teacher? How do I know?

It seems like a simple enough question, am I a good teacher?  The question however is not so simple.  Education is an area that is both measured and researched extensively so your impact as a teacher can be measured, compared and analysed in any number of ways, but what measures do we value most and which measures best define us as teachers.

I have been teaching now for 12 years.  This is long enough for a student who started their schooling to now be at the stage where they are completing their schooling.  I have taught a lot of students in a lot of subjects, some of these students have now been in the workforce for long enough to reflect on school at the time.  I want to share some of the seemingly contradictory impacts of some of my current and my former students

• One of my students from about 8 years ago who never really did much in class saw me standing outside a shop that he was working in. When he served my wife he said "Mr Loader is a good bloke, I never really did any work in his class, but he never gave up on us like others"
  
  
• One of my former students from only a little while ago told another teacher "if you want to make kids like maths, to make it interesting, speak to Mr Loader, he knows how to make people want to do maths."  this student produced some excellent work in class, but in the diagnostic testing their score improved but not by as much as their work in class had improved.
  
  
• A number of my former students have shown massive increases in their scores when looking at their diagnostic assessment.  However they had not done much at all in class at any point during the year and have said that they don't like maths as much as they did previously.
  
  
• I do a lot of research on trying to understand what the evidence base says about effective practice.  I implement it, it works (at least in my eyes), it seems to improve the learning in the class and then I see no gain in the results or find another piece of research that contradicts it.
  
  

Now these are just a few that I have chosen to pick on but the message is the same, sometimes, but only sometimes, all the data sets align and we see growth in achievement, attendance, engagement, diagnostic testing, behavior, perceptions etc.  Most of the time however seeing gains in some areas means having at least temporary setbacks on others.  either because the results are already high and therefore can't really change much or because introducing something new or different causes them to work and see the subject differently.  How do you gauge your impact when some in the class are really enjoying and gaining a lot out of what you are doing and others hate it and are not doing much, can we only say we are having an impact if it is occurring for everyone in every class.

Looking back at some of the examples above, which of the criteria in each example above do I use to measure my worth as an educator.  Is it that I place more emphasis on the fact that some of my students are just not doing any work and therefore I am not doing a great job, or do I place greater emphasis on the idea that a student knew I would never give up on them.  Do I place more emphasis on the fact that test scores have not improved, or do I place it on the fact that students are gaining a real love for mathematics as a result of my teaching. Do I place it on a huge increase in test scores despite no work being done in class and the student disliking the subject more than they had in previous years. How do I reconcile what these contradictory bits of evidence say about me as an educator? Do I see these contradictory bits of evidence in a different light to how others see them?  Do I value only what can be measured or do I value more the stuff that cannot be measured?  How do I truly know my impact as a teacher?