" Reid schooled everyone in the office."
Nice, Reid. In this sentence, the verb school selects for one object: they which were schooled, or everyone in the office. Since the action is happening directly to the object, it's a direct object.
" Jonathan slammed the birthday cake on the ground."
In this very unfortunate sentence, the verb slammed selects for a direct object, which is the birthday cake. The verb "slam" is a bonafide transitive verb. The act of slamming here needs something to receive that action; otherwise, it's totally weird. "Jonathan slammed"? Sounds like a cheap knock-off of "Hulk smash."
We don't think so, Jonathan.
" Kenny roundhouse-kicked the door."
Looks like Kenny the karate kid has some anger issues. In this sentence, the verb roundhouse-kicked selects for the direct object, the door.