ACT stands for
American Conservatory Theater, a
regional theater company and an
actor training school based in San Francisco.
According to their website, Denzel Washington, Annette Bening, and Winona Ryder studied there.
ACT's classroom offerings include a Young Conservatory program for ages 8 to 19, a Summer Training Congress, and an MFA program.
ACT's Geary Theater is probably the best-known and best-respected spoken-drama (i.e., not ballet or opera theater in the Bay Area), not counting theaters that serve touring companies.
Albert Bowker is a season subscriber, as are most of the Bay Area elite and ex-elite, I imagine.