“Going by the _________ that many hands make light work, the school _______ involved all the students in the task.”

The words that best fill the blanks in the above sentence are

The correct option is principle, principal.

To determine the correct words for the blanks, let us look at the meaning and usage of the homophones "principle" and "principal":

1. First Blank:
The sentence starts with: "Going by the _________ that many hands make light work..."
Here, we need a word that means a fundamental truth, law, rule of conduct, or general belief (such as a proverb or saying).
- Principle (noun) means a fundamental truth or proposition that serves as the foundation for a system of belief or behavior, or for a chain of reasoning.
- Therefore, "principle" is the correct word for the first blank.

2. Second Blank:
The sentence continues: "...the school _______ involved all the students in the task."
Here, we need a word that refers to the person who holds the leading or most important position in a school.
- Principal (noun) refers to the head of a school, college, or chief administrator.
- Therefore, "principal" is the correct word for the second blank.

Combining the two explanations, the words that best fill the blanks in the sentence are principle and principal, respectively.