Pronoun Antecedent Agreement
Pronouns stand in for or refer to a noun. Therefore, pronouns not only need to agree in number, but they also need to agree with the antecedent, the earlier word or phrase to which the pronoun refers.
In this example, “student” is the antecedent. Since student is singular, the pronoun needs to be singular. When we know the gender of the student, then we can rewrite the sentence correctly:
You can also take the original sentence and correct it by making the subject and object plural:
Some pronouns, like each, anybody, everybody and someone, will always be singular. Therefore, they will agree with a singular pronoun.