Although I retired from public high school teaching last June, I feel that Aug. 31 was my first day of actual retirement. On that day, my former colleagues returned for workshops and to prepare for another busy year. I wish them all the best, but before I become a total outsider, I wanted to share with the rest of you a few thoughts, based on my 32 years in the trenches.

Teachers work really hard: That's probably why they don't answer your e-mails right away. On a typical day, I would arrive at my building an hour before the first class (usually with students already waiting to get help), and I don't think I came up for air until my 20-minute lunch. And then I'd stay at it until an hour after the last class was over. During five of those hours each day, I needed to be totally "on," making what amounts to a presentation for 35 (40?) young people who may or may not have been excited to be there. I needed to be organized, convincing and facile with any technology being used. The radar would be constantly going — monitoring learning, adjusting the plan, and noticing and dealing with off-task behavior. Then, when the hour was over, there'd be five minutes to reboot.

I usually worked 60-hour weeks. That number times 38 weeks per year gives 2,280 hours per year. Now, tally up your hours per year and compare, and then please don't tell teachers that they get "lots of time off." You probably get more.

Teachers can actually be fired: Educators say that once something is learned wrong, it's really hard to unlearn it. One case might be rubber tires protecting you from lightning, but another is about teachers and how they can't be fired. I have seen plenty of teachers let go, or fired or counseled out of the profession during their three-year probationary period. The process is not complicated, and it amounts to a very effective filter for people for whom teaching is not a good fit. The teachers who are retained after probation have shown themselves to be at least proficient, if not outstanding teachers, and a district is probably only too happy to grant them tenure.

And I just used the "t" word, which would seem to be naughty in some circles. Tenure doesn't mean a teacher can't be fired — it just means he can't be fired for a capricious reason. You can't fire a teacher just because he's gay, or an atheist, or gave the mayor's daughter an F and won't change it. None of these has any bearing on the teacher's ability to teach. If he's no longer a good teacher, then he can be fired, but now there's a contractual process to make sure the firing is done fairly and transparently.

And I have seen this happen. It doesn't happen very often, because, honestly, most teachers take their responsibilities very seriously and spend a career discharging them well. The firing rate for tenured teachers is about 2 percent, roughly the same as the rate for experienced workers in the private sector.

That achievement gap — it's complicated: Yes — I just saw the ACT results, too: 23.7 for whites, 19.8 for Latinos and 17.6 for blacks. I take issue with those who feel that if teachers just did their job better, that achievement gap would go away. During my teaching days, each student spent about seven hours in my building. That leaves 17 hours in any given day, and those are the make-or-break hours, as far as I'm concerned, regardless of ethnicity. Hopefully, when those 17 hours start, every kid goes home to a stable, loving, nurturing family that places a high priority on education and one that has the means to provide, among other things, good nutrition and health care. If one or more of those ingredients are missing, that could affect a test score, and an overall education, far more than a teacher ever could. Education must start, and be constantly reinforced, at home.

As I close, I feel very grateful for the career I've had, and I hope that students and teachers alike have a challenging and rewarding year.

Mark Brandt, who taught physics, lives in Minneapolis.