Passive verbs always include some form of the verb “to be” (including “was”), but that doesn’t mean all uses of “was” are passive. That’s a bit like saying all cakes include eggs; therefore, any recipe with eggs will result in a cake. Like the egg, “was” has a variety of uses. For example, it can act as a linking verb:
He was a teacher.
And it can be part of a past progressive construction, which shows something happening in the past at the same time something else happened:
She was running down the stairs when the subway pulled into the station.
So how do you know when a sentence is passive? When the subject doesn’t perform the action; instead the action is done to the subject. For example:
He was chosen by the team.
That same sentence would become active by making the subject the do-er of the action:
The team chose him.
While “was” is commonly seen in passive voice, other forms of the verb “to be” can create passive voice, too. For example:
The peanuts will be shelled by Ann.
(Active: Ann will shell the peanuts.)
So don’t automatically implicate “was” when it comes to determining passive voice. Look at the role of the subject: Is it doing the action? Or is the action being done to it?