[bsder]

> Why are big changes not arrived at by first gaining experience with them in in some reduced scale

Because the results that come back are always politically inexpedient to agendas--generally for all sides.

Examples:

1) Charter schools: As soon as you force charter schools into an actual lottery which normalizes their student body relative to the public schools, their performance relative to the public schools craters. Quelle surprise: Expensive students are expensive and take up a disproportionate amount of your smaller budget. Quelle surprise deuxième: motivated parents means better student performance.

2) Low end performance: low performers actually make up some of the gap during the school year. This creates the obvious suggestion of year round school which runs into the fact that would require an immediate 25% pay raise to every teacher.

3) Raising the average/median: Even the Gates foundation documented the solution but stopped short of suggesting it--focus most of your resource on the lowest performers as they are the easiest to improve. I don't even have to suggest the firestorm that causes.

4) Proper student:teacher ratios: Again even the Gates Foundation (whom I loathe) documented it correctly--1 classroom with 2 credentialed teachers (randos aren't enough) per 15 students (middle and elementary was the focus--high school is a bit different). Every program that followed that formula had solid documentable success. Every single program that followed that formula got closed for being "too expensive".

I can go on and on. The problem is that the US education system is at a solid local minimum and getting out of it requires significant amounts of focused resource. And when you finally ask folks to start writing checks for your education system, you suddenly find out exactly how much folks want to improve education (aka nothing for teachers or students, but they'll happily fund that new stadium).

And, I would like to point out that it was school spending that went up by 45% more than inflation (which was 35% over the same period). In addition, teacher salaries didn't go up 45% relative to inflation. So, might I suggest that perhaps the problem is what we are spending the money on?

[zozbot234]

> focus most of your resource on the lowest performers as they are the easiest to improve

That depends heavily on the pedagogical approach. There are approaches that are quite effective in bringing low performers up to near-par (so-called "direct instruction", in a broad sense) but teacher actively hate them because they're viewed as "demeaning" the profession, and ed schools don't teach them. Special Ed teachers actually get extensive instruction in these approaches, but obviously we cannot and should not treat every low performer as Special Ed.

> Proper student:teacher ratios

What's "proper"? Teacher-centered and direct approaches cope quite well with greater class sizes, but again they're unpopular among teachers.

[bsder]

> Teacher-centered and direct approaches cope quite well with greater class sizes, but again they're unpopular among teachers.

Cite. All research I have seen completely contradicts this.

The limitation with larger class sizes is not "knowledge transfer"; it's "classroom management" aka dealing with a student causing an interruption for some reason (bathroom, injury, sickness, etc.).

I use the Gates Foundation as my primary citations because they are easily findable on the web and simply match all of the other findings. You max out at about 15 students per 2 teachers because one of the teachers can handle the inevitable disruption while the other teacher can continue teaching. The more students you add on top of the roughly 15, the more likely you wind up with 2 interruptions which stops the class cold irrespective of teaching technique.

And, as I have stated, most of the research focuses on elementary to middle levels. High school requires teacher specialization which confounds a lot of the data.

[zozbot234]

How Does Class Size Vary Around the World? (OECD, 2012) shows that there are countries such as Japan and South Korea with some of the largest average class sizes, and excellent educational achievement. Clearly it's far from the only or even the most important factor. The United Kingdom is one country that skews the other way, though there are countries like Estonia with similarly small classes that seem to do a lot better.

[Nevermark]

I know nothing about those countries ratios.

But on the topic, I suspect the best time to have high teacher ratios is in the earliest years. Help children learn to manage themselves, focus, follow through, etc. Then work up to large class sizes in the upper years.