The math change was as you remember, but I definitely remember physics and chemistry 10 even after the change (Rockyview).
My grade 10 year was the year the changes took effect. However, since I was advanced a year on math, I took Math 10 in grade 9, so accumulated credits before the change. When I graduated, the government sent me an advanced diploma. A few weeks later I was sent a regular diploma and told to shred the advanced because I shouldn't have gotten it. (
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I don't remember all the reasons for the change, but mostly I think it was the same as why some teachers mark in purple pens instead of red these days: fear of upsetting precious little snowflakes and their parents because their kids aren't as intelligent as they think.