A. "...'Take one psychology class and you know everything. You need to go on back to college...'"
Participles are verb forms which look like verbs + suffix -ing. So having that in mind, the participle in the sentence above is the word standing.
Participles function either as adverbs (when they modify verbs), or as adjectives (when they modify nouns). In this case, the participle acts as an adjective, modifying the word child.
Well, probably just to make the story interesting.
