I used to be a schoolteacher, so whenever I read about someone's shiny new EdTech idea, I can't help but think that it's a tarpit idea.<p>Every developed country has a set of professional standards for teachers, and teachers who don't live up to those standards are pushed out, sometimes by having their teaching accreditation revoked. In Australia, for instance, there's a set number of hours of 'professional development' that teachers have to do every few years, and if you don't complete them, you lose accreditation and have to find a new career. The professional development activities and courses that meet the requirements are audited by the Department of Education, and have to draw on the latest research in educational psychology: keeping up with the latest research is the entire point of that professional standard.<p>When I did my teacher training, the first thing we were told in the first lecture was to never cite any research older than ten years, because it would be out of date. Now, if you've trained in the sciences - I was a physicist - you should be troubled with this, because a discipline can't really accumulate knowledge about the world if it throws everything out after ten years. That's why, when I broke the rules and searched through the databases of academic literature going back more than ten years, I saw the same ideas being reinvented under different names in different decades.<p>So there seems to be a bit of a trend for people to build flashcard-type tools at the moment, probably because someone's seen a paper on spaced repetition. That's nice, but you can't build a business around this. It doesn't matter if all the thought leaders are all in on spaced repetition this year, because next year they'll have moved on to something else, because they need to have something new to talk about. In Australia and the UK at least (I don't know the figures for other countries), half of all teachers leave the profession within five years of joining it, so most of your user base is overenthusiastic twenty-somethings with no life experience (yes, I was one of these) who will do whatever The Research tells them, and the ones who stay long enough to gain leadership positions tend not to grow out of this, so the classroom side of EdTech is basically a bunch of fads, so it's impossible to build a stable business in this space.<p>If you want to sell software to schools, go and work in a bunch of them, find some obscure administrative problem, and solve that.