Builders, meat-cutters, plumbers, electricians, surgeons, and so on, usually get to see the results of their labor and expertise relatively quickly.
Teachers are among those who may not see the fruits of their work right away and who, indeed, can never be certain about what effect they have had.
I'm thinking about this because I traveled to Portland to read some poems to some alumni from the college where I have taught for quite a while, and simply to chat with the alums. (I insisted on titling the evening "Just Enough Poems," conscious that poetry in general and my poetry in particular may be an acquired taste.) I'd not had some of them in class; others had taken one or more classes from me.
--An impressive group, and to back up "impressive," one is tempted to name occupations: doctor, wine-maker, pub-owner, drama-teacher, parent, businessperson, etc. But more impressive is the sense one has that these are good and complicated people--thoughtful, well read, responsible, intellectually adventurous.
Many of them still write--as they are fulfilling other responsibilities and pursuing other professions. That is impressive. Also, these sorts of writers--the ones who are not famous (yet), the ones for whom writing is just one piece of the puzzle--may be more crucial to a culture than the writers on whom all the light is shed.
--But back to the original thread: a teacher a) often has to wait decades, not just years, to have some sense of what effect he or she may have had on students and b) still cannot and indeed should not be tempted to take credit. There is rarely any way to prove that one's teaching led to any student's impressiveness. That is as it should be, not just because this circumstance reins in a teacher's pride, but also because the circumstance reminds a teacher that teach8ing is an art and an act of faith.
Nonetheless, the alumni I talked with and read poems to are impressive in the right ways. They are decent, smart, accomplished people. They are nobody's fools. To be nobody's fool is one great potential result of education, in my opinion--and a result the teacher should be reticent to claim credit for.