Which sentence uses semicolons correctly?
teenagers often attend school, have jobs, and participate in after-school activities; such as sports, theater, and band.
teenagers often attend school; have jobs; and participate in after-school activities; such as sports, theater, and band.
teenagers often attend school; have jobs; and participate in after-school activities, such as sports, theater, and band.

The sentence that uses semicolons correctly is, "Teenagers often attend school, have jobs, and participate in after-school activities; such as sports, theater, and band". A semicolon is used after the word activities to separate two different series of words in the sentence. To avoid confusion between the series that describes what teenagers often do, and the series of examples of after-school activities, the semicolon is being used.