SAN FRANCISCO (CBS.MW) -- As many people suspect, the path to the Ivy League is most successfully traveled through exclusive private schools.

Of the 100 U.S. high schools sending the highest percentage of students to Harvard, Yale and Princeton, 94 of them are private schools -- with tuition ranging from $7,800 to $29,650 a year, according to a study by Worth magazine.

There's no doubt guidance counselors at private schools have more time and resources to better guide students to college. But counselors say the Ivy League draws heavily from top-notch private high schools because most of their students had to beat out their peers academically to gain admission at that level.

"Our school takes one out of three applicants ... and what criteria do you think they use?" said Jon Reider, director of college counseling at San Francisco's University High School, No. 35 on the list. "They use academic and intellectual criteria so they are likely to have a class of students who are very academically talented."

But not all is lost for the two-out-of-three applicants who don't get into University High, or for those turned away or unable to afford other costly private schools.

More than half of Yale's undergrads are public-school alumni, said Yale spokesman Tom Clancy. Harvard's online guide says two-thirds of its undergraduates are from public high schools. And Princeton spokeswoman Marilyn Marks said "a majority" of that school's new admits last year were public-school students. And, Marks noted, the 2002 class valedictorian was home-schooled.

Still, those parents dead-set on getting their kid into Harvard, Yale or Princeton may want to consider moving to the Eastern seaboard. New York and Massachusetts are home to the top 10 schools on the list, which send between 16 and 21 percent of their students to one of the three colleges. Of the top 30 schools, only one is not in an eastern state (it's in California).

The Worth magazine survey also ranked the top 50 U.S. public high schools that feed students to Princeton, Harvard and Yale. Twenty of those schools are in New York, and 13 are in Massachusetts. See Top 100 and Top 50 public lists.

One public school -- New York's Stuyvesant High School -- sends only a small portion (3.67 percent) of its total students, but makes a strong showing in real terms. A total of 113 Stuyvesant grads were at one of the three colleges in the years studied, putting it third overall among both public and private schools. Phillips Academy and Phillips Exeter Academy had 167 and 153 graduates, or 15.68 and 14.75 percent of their students, at those colleges, according to Worth.

There are options for parents whose kids are not likely to go to one of the top-ranked schools. Simply having dinner-time conversations can help spark the intellectual curiosity that leads to the sharp high-school performance colleges seek, Reider said. Once kids are in high school, encouraging them to take honors courses, or even just an extra class, can mean better-looking transcripts, he said.

"Go beyond the requirements. Some high schools aren't demanding: Make it more demanding. Read an extra book, do an extra project. That's what private schools do," Reider said. "If you as a parent can help your children develop that intellectual curiosity you don't have to spend millions of dollars on it."