10/17/2008 at 07:10 PM EDT
stopped by a Los Angeles elementary school as a special guest speaker, but she wasn't there to discuss Hollywood.
"She talked about water things," says Alvaro Cortes, assistant superintendent of Extended Day Programs at the L.A. Unified School District. "She talked to the students about water nutrition and why it's so important for all of us."
Aniston, 39, a spokeswoman for Smartwater, a nutrient-enriched bottled water, stayed at Cahuenga Elementary School on Thursday for about an hour and answered questions as part of an after-school program.
Along the way, she even got a little education of her own. When she showed up a few minutes late, principal Lloyd Housky said, "As a school principal I need to tell you that you cannot keep our children waiting!"
Aniston replied: "I understand! I got that message from my principal when I was going to school, too!"