The correctly punctuated sentence is:
Art; Brenda; Clavin; and I are attending tomorrow's band and choir concert.
However, please note that the use of semicolons here is unusual, as semicolons are typically used to separate items in a list when the items themselves contain commas. Since "Brenda" and "Clavin" are not complex items, a simple comma would suffice in most cases:
Art, Brenda, Clavin, and I are attending tomorrow's band and choir concert.
This alteration would be standard punctuation if no additional context requires semicolons.