Rewriting a Sentence Using Reflexive Pronoun

A reflexive pronoun refers back to the subject of a sentence, or the subject of a clause. The subject always comes before the reflexive pronoun.

Reflexive pronouns are used when both the subject and the object of a verb are same. Hence, they should match with the subject.
 

Subject (singular)	I	you	he	she	it
Reflexive pronoun	myself	yourself	himself	herself	itself

Subject (plural)	we	you	they
Reflexive pronoun	ourselves	yourselves	themselves

 

The teachers	held	themselves	to high standards for student achievement.
(s-u-b-j-e-c-t)		(reflexive pronoun)

The subject of the sentence is the teachers. Since the teachers could be replaced with the third person, plural pronoun they, so the correct reflexive pronoun is themselves.

Hence, themselves is used to replace the teachers as the object of the verb, held.