what would happen in a regular school lab if the standard for mass was one of the two natural phenomena?

Answer 1

I assume you mean what if we chose some other 'standard' to 'one pound' ?

Well all the other measurements would have to fall into line, but the short answer is 'not a lot'.

FYI - in Europe the standard is defined as 'one kilogram' - and they still have high school physics :-)