Should you have any interest in teaching students to write letters (I think you should, though also recognize that you needn’t if you so choose or are teaching to tests), you might find this context clues worksheet on the noun salutation and this one on the noun valediction useful in introducing these two concepts vital to letter writing to your students. You could also use them as they are, or rewrite them, to introduce the words salutatorian and valedictorian to your graduating seniors.
If you find typos in these documents, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.