An Adjective Question: Excited, Tired vs. Exciting, Tiring, etc.

Why is the past participle used instead of the present participle?

I went to an elementary school. I was excited.

Why is the present participle used instead of the past participle?
I taught children. It was exciting.

First, these sentences are both S, V, SC, right? Or are passive voice or another grammar structure playing a role?

If they are not, why does the adjective verison of "excite" change?
(Other words with a similar usage: tired/tiring, bored/boring, dissapointed/dissapointing, enjoy/enjoyable, interested in/interesting,etc)

At first, I thought it was due to emotions--events and things can't have emotions. A job can be exciting, but it can't be excited. People can be excited. However, some words work in both situations. Why? Example: "I was sad." "The movie was sad."

Are there shorter versions to these sentences? I was sad at the movie. The movie was sad to me. Meaning-the movie wasn't taking on an emotion after all-it was reflecting my emotion. Or...can a movie be sad grammatically?

Also, I'm excited. I am exciting. The meaning is different here.

I'm feeling excitement vs. I produce excitement. Why does one use the past participle and the other the present participle?

Thanks a lot. I'm really interested in your responses.
Chris