In 6th grade we have entered the realm of passive voice. This is a good age to get them thinking about the difference between active and passive. I have them act out active: pretend you're a superhero (teacher cues them by assuming a charging super-magistra pose, one arm extended). Active voice happens when the subject performs the action of the verb. Now pretend you're roadkill (all 6th grade students naturally want to mimic roadkill for some reason). Passive voice happens when the subject receives the action of the verb. As a general rule, it is better for young people to be active than to be passive. These are smart kids: they can think of plenty of examples. As we work through the sample sentences in Henle Latin I, an informal survey indicates that the majority of passive voice sentences are negative for the subject.
We memorized the passive voice endings for the present system:
r, ris, tur, mur, mini, ntur -- present system passive (repeat)
... to tune of Yankee Doodle
If you want to tell who is performing the action in a Latin sentence that uses passive voice, you have to use the ablative of agent. I had a student ask yesterday what agent means, and I found a very opportune example. Secret agents, like the ones who killed Osama Bin Laden, perform lots of actions. The word "agent" comes from the Latin verb ago, agere, egi, actus meaning "do, drive, act, or treat" (which also gives us the word "actor".) To be technical, "agent" is derived from the present active participle of ago, and literally translated means "acting person."
Sample sentence, improvised on the spot:
Osama bin Laden superabatur ab agentibus. Osama bin Laden was conquered by the agents.
(we can only do passive voice of 1st conjugation verbs so far: occido "kill" is 3rd -- but you could substitute occidebatur.)
See? Osama is the subject, and passive voice is definitely a bad thing for him. But very, very, good for the agents.