All of the middle and high school math educators I´ve encountered choose not to use LaTeX in preparing their documents or presentations. I would assume that most of them had to use the program in the past for their Bachelors or Masters programs. What are some reasons why it is not used before the undergraduate level?
When I taught high school, I used mathtype to type up all exams. There was a trial version and a discount for teachers. I learned about mathtype at an NCTM conference.
At other times I used equation editor in Microsoft word and math tools for the smartboard (which meant I could type up things on my computer at home as long as I used the smartboard software. I learned how to use the smartboard at various workshops I went to as well as an online course.
I never used Latex for three reasons:
1. the tools I had were adequate 2. I never heard of Latex until I joined this forum (NCTM doesn't mention it anywhere) and never had any training. 3. The tools I had were considerably more intuitive than Latex
Finally, in response to one of the comments, I don't consider it sad that I never used Latex.
(what follows was assembled from several comments, now deleted)
At least in the U.S., once you get away from academic research environments that are strongly connected to math, and you become immersed in environments such as academic education departments, academic business departments, education administration, pretty much any business or financial setting, even the preparation of math questions for standardized math tests, you'll find essentially zero official use of LaTeX. Even the journal The Mathematics Teacher, which by a wide margin is the best known and most influential journal in the U.S. for middle and high school math teachers, strongly desires manuscripts written in MS Word with MathType. Thus, to answer your question, the middle and high school math teachers you’ve encountered probably have had very little contact with anyone using LaTeX.
That said, there is at least one alternative that does not involve as steep a learning curve as directly coding LaTeX, which incidentally I did when writing my dissertation (1993, 200+ pages with many complex math expressions), something I did by making heavy use of Leslie Lamport's 1986 spiral bound manual LaTeX. A Document Preparation System. Because I did not have access to a computer or any software the 18 or so months after Summer 1993, I still hand-wrote tests and handouts and such (as I'd always done, since the first class I taught, Summer 1983). However, a colleague had Scientific Word (Version 2.0, I believe), which is a wysiwyg format for LaTeX, and I "borrowed it" (installed it on a 386 PC computer that I had just gotten use of from the math dept., around Jan. or Feb. of 1995 I think) to write some math papers and other documents (but not yet for any classes I taught). Beginning in Fall 1996 I was teaching somewhere else, where at that time faculty did not have computers (this changed a year later), so around October 1996 I purchased my first computer and Scientific Workplace (SWP) for it (Version 2.5; had a computer algebra system attached, my first ever use of one), and at that time I began writing what eventually became several thousand teaching documents (quizzes, tests, handouts, etc. --- I posted a few of them before this option at Math Forum became unavailable) that I had written by 2005, when I left teaching.
I upgraded my 1996 Scientific Workplace program to Version 5.5 in Summer 2013, and I probably spend at least two hours with it each day (often more) working on various documents and such. However, I DON'T use LaTeX the way others here probably do, because the symbols are all pop-up and easy to use --- much easier than MathType (and looks much nicer also), and trust me, this is not because I don't have much experience with MathType (for the past 12 years my full-time job involved using it extensively; or see this). The main downside is the cost, which is about 800 dollars (386 dollars for students). I paid around 400 dollars in 1996, although at the time I believe the actual price was 600 dollars, but in my dealings with the company I think they were hoping --- indeed, they basically told me this --- that my use of SWP would result in the school buying a site license, so they were willing to knock off a couple hundred dollars.