Which sentence is correct?

Question

One third of the schoolday is spent taking unimportant tests.
One-third of the school day is spent taking unimportant tests.
One-third of the school-day is spent taking unimportant tests.

Answer 1

The correct sentence is:

One-third of the school day is spent taking unimportant tests.

This version correctly hyphenates "one-third" and leaves "school day" open, as "school day" is a compound noun that does not require a hyphen.