That method has worked well for 100's of years. Why anyone would change how math is taught is beyond me. Teaching New Math really pissed me off, "set theory" to grade schoolers? Really? Fools. Just pound arithmetic into their little mushy heads first. Once they can do long division competently then we can move past arithmetic. Not before.
>> “Why anyone would change how math is taught is beyond me.” <<
Are you old enough to remember “SMSG?”
That was when the US began its descent to the bottom.
They are teaching so that kids can’t learn. Want to see something REALLY scary? This is why kids can’t do math.
https://www.youtube.com/watch?v=wOH9gwImyXg