I took Algebra in the 9th grade.....
Algebra I, Algebra II, Geometry, Trigonometry and Calculus were all required before high school graduation.
Why are colleges teaching Algebra?
Ditto here, more or less. (Algebra II introduced calculus). In my high school you had to take these if you were college bound.
I think there has been college algebra for a very long time, what is new is college classes preparing students for college algebra.
Where and when on earth were there such requirements for a HS Diploma?