The guys who taught me the most in classes were those who themselves had to arrange stuff. There was a professor / teacher at Stanford who taught orchestration and who did all the arrangements for the marching band (so-called; Stanford's band doesn't "march;" it swarms, or something). That guy was practical.
The other guy was a composer named Don Ray who'd started writing for TV back when electronic instruments were expensive, hard to use, and often not very portable. So he knew how to write for a small ensemble and still make it sound interesting and give it variety.
It's a lot easier to have variety with 90 players than with, say, 11!
Standard Curriculum(?)
The point to this missive is that in general, universities are not packed with actual practitioners -- people who write, day in and day out, for ensembles of any size. Consequently, I am not aware of a "standard curriculum" for teaching practical orchestration. I'm not even sure it exists(?) There are books, some of them quite useful, but that's about it, methinks.
I learned what I know from two things:
1. Reading scores (including some of the scores that those guys used as sources); and
2. Orchestrating for other guys and then hearing it week after week. Quite a set of lessons that was!
I also was lucky enough to work quite a while with Immediate Music, who hired large orchestras for trailer music. It was awesome.
Oh yeah you're totally right. There isn't really a standard curriculum. Although I personally think there are basics that EVERYONE should teach. Voicings, part-writing, harmony basics, arranging (so you actually know how to use the ideas you have), instrumentation, melody development, etc. For instance some of the most basic things people say about arranging I was never taught. For instance: make something new happen every 2-4 bars, each section should have some contrast, NEVER make all of the instruments play all the time because tutti sections get old very fast. These are for sure guidelines, but they can get you quite far imo. Hell even just having well written part-writing makes SUCH a big difference haha.
The kinds of things you read in an arranging text within the first 30 pages. I learned similar to how you did. Mostly score reading, and writing for people outside of school. My comp professors were a mixed bag. One mostly wrote for 20th century orchestra, while the other was very into new age electronic music. So I'm sure that's a big part of it. They had already learned all this stuff and discarded it.