Your teachers are bad at their job. There is nothing wrong with that method. Now, if you also try to do 7+3 as 5+5, you might need to learn other method so next time, you choose a more efficient one. But against that would not be wrong.

[–] bizarroland@lemmy.world 3 points 5 days ago

Especially since the thrust of the new math curriculum seems to be more about being nimble with numbers and being able to conceptualize and compartmentalize their values rather than learning rote formula.