Ammini and Daniel Cherian were proud when their eldest daughter was tapped to be a valedictorian.All her hard work had paid off, they thought.Three years later, their second daughter earned the same honor."Oh, she also made it,'' they said, relieved to have another recognized for her efforts.And their reaction when their youngest daughter was named a valedictorian?"We weren't surprised,'' said Ammini Cherian.Others, though, are impressed.The Cherian sisters — Karen, Christina and Cheryl — all were first in their class in Hillsborough High's challenging International Baccalaureate program."I have never in my 18 years of teaching heard of three sisters holding that spot down in such a rigorous academic program as ours,'' said history teacher Tom Paloumpis, who taught all three girls. Everyone asks the Cherians, "How did you do it?''"Always,'' Ammini said, laughing. "They want to know, 'What do you feed them? What do you give them?' ''There's no secret formula, she said.Her daughters credit their parents, South Indian immigrants who came from humble means but believed in the value of education."I think we were able to give them good basics,'' said Ammini, a clinical nurse educator at Tampa General Hospital, where her husband is a systems analyst."We always made sure they were doing their work. But we didn't have to push them much.''Cheryl, like her older sisters, eagerly juggled advanced-placement and college courses while fulfilling her IB requirements.That allowed the 17-year-old senior to rack up college credits and an impressive 8.56 GPA, though she estimates it will be closer to 9.0 when calculations are complete.Higher than Christina's 8.12 in 2008 and Karen's 7.64 in 2005 — the highest grade point average that year in the Hillsborough County school district.There's no sisterly rivalry, though."I think we just competed against ourselves,'' said Karen, 24, who graduated recently from the University of Miami's medical school. "We always wanted the youngest sibling to do better.''Sometimes, the big sisters had to remind the littlest one to take it easy."Because you don't get these years back,'' Christina said. "It's important to work hard, but it's more important to stay sane.''The sisters gave their all to realize their talents and abilities, Paloumpis said."I do not know if driven is the best word,'' he said when describing their study ethic. "More like a quest for learning, and wanting to always do their best.''They grew up hanging on to every word of Mom and Dad's hospital stories, so it was no surprise, again, when the trio decided to share the dream of medical school.Karen begins her residency this summer at Bayfront Medical Center in St. Petersburg. Christina, 21, just graduated from the University of South Florida and starts medical school there in the fall.Cheryl plans to attend Penn State University and its six-year medical program. "I'm really lucky,'' she said. "My parents let me be who I am. They let me do what I wanted to do.''She is also the last of the Cherian siblings, marking the end of the valedictorian victories.It "will be weird not to have a Cherian,'' roaming the hall, Paloumpis said.