When girls dance better than boys. Girls dance better than boys. Became plural, why did the dance become singular?

When the girl is the subject, the subject is a third-person singular (he, she, it), using the third-person singular form of dances.

Dance means dancing here, but it is a verb. Verbs cannot be singular or plural.

In the case of the simple present tense, there is a third person singular form (s/es).

He goes to school on foot.

Variable complex number

They go to school on foot.