or something called UICSM (University of Illinois Committee on School Mathematics). I chose UICSM.
It was AMAZING!! We discovered everything. In the geometry part, (which lasted a semester because that's really all the geometry you get the first time around) we were given (if I recall correctly) four postulates, and derived everything else, meaning all the theorems, from them.
I took 3 years, at the end of which we were well into calculus, which I quite frankly was having a very difficult time with.
Fast forward some 30 years. I'm trying to get into a degree program at the University of Kansas that required math through college algebra. So I went to the math department at my junior college and promptly tested into algebra 2. After 30 years of no math classes. I did well in algebra 2, even better in college algebra. I decided to take statistics as I knew it could be useful for the degree I was planning. That was so much fun that I decided to take calculus. I'm probably the only woman who ever took calculus for fun at age 43.
All during those courses, I'd sit in class and specifics from high school UICSM would bubble up in my head. Things, such as something is only true "if and only if" something else is true. I asked one of the math teachers at my community college about that phrasing and was told that kind of language is typically used in much more advanced classes.
In all of the decades I've been telling people about UICSM I'm yet to meet someone who has even heard of it, let alone taken or taught it. I suspect the reason it went away is that it would have been a much more rigorous and difficult class to teach, compared to traditional math. But oh, dear lord, I learned a lot. Thanks to the amazing and wonderful Clifford Haugh who I had for years 2 and 3 of that program.