Seventy thousand young hopefuls turned up in long lines in several cities last year to stuff themselves into auditoriums and stadiums in hopes of being anointed the new "American Idol" in the smash hit Fox television program. All but a few hundred never got past the initial screeners, and nobody but the last dozen finalists got much time on TV.

The same number of young hopefuls, 70,000, are receiving letters from Harvard University this year inviting them to participate in a competition with a similarly high failure rate. The letter sent to each recipient, selected mostly on the basis of test scores, says "congratulations on your academic achievements" from America's oldest university and urges them to apply for the class of 2009.

The "American Idol" contestants mostly knew how lousy their chances were. They had seen the show before and realized that almost no one got anywhere near Hollywood. But the impressionable high school juniors who are persuaded to apply to Harvard this year because of the unexpected attention from its admissions office are going to be less well informed of their chances.

Nowhere does the Harvard letter tell them that the school is only going to admit about 2,000 applicants, even though it has sent its letter to 35 times as many. Nor does it say that the school's energetic marketing of itself, common among selective colleges, has brought it record numbers of applicants -- usually about 20,000 a year -- and led it to reject 90 percent of them, year after year, including most of those who responded to its kind invitation to apply.

Many colleges send out even more letters than Harvard does. The University of Pennsylvania has mailed 80,000 of its missives telling each recipient that "you're likely to be a strong candidate for admission at some of the nation's finest colleges and universities." Yale University won't disclose how many of its welcoming postcards it is sending out, but the number is likely to be about the same as its Ivy League competitors. In each case Yale tells the lucky teenager it wants "to recognize your impressive academic record."

The colleges deny they are adopting the worst habits of modern marketing, but it is hard for many of the young applicants who are courted and then dumped to see the difference. The "American Idol" producers are pandering to the dreams of the nation's youth to pump up their television ratings and secure big advertising and music sales revenue. That is why they were in business in the first place. What's Harvard's excuse?

Schools that send out the most search letters -- 75,000 from the Massachusetts Institute of Technology, 100,000 from Virginia Tech University, and untold numbers from really aggressive mass mailers such as the selective Washington University of St. Louis -- say they are trying to encourage students with good grades and test scores who might otherwise be intimidated by their famous names or large tuition fees. They say they are addressing them only to students whose scores on the PSAT, SAT, Advanced Placement or ACT tests are high enough to make it likely they will get into some good college. They often urge low-income students to consider the possibility of financial aid, and Harvard reminds its recipients of a new policy waiving all college expenses for families making less than $40,000 a year.

Reaching out to high schoolers this way has become a big business. About 1,400 colleges buy the names and addresses of high-scoring students from the College Board, which takes them from tests of students who have given permission. On average each college buys about 45,000 names, at 26 cents per name, or $16 million for the nonprofit College Board, which says it plows the proceeds into other student services. The colleges also earn considerable revenue from the application fees of the students who accept their invitations.

Most American colleges admit nearly everyone who applies. For them, a big mailing campaign creates no false expectations. But it is a lot to ask a 16-year-old to understand why an Ivy League college sent her a very literate love note her junior year and a much less friendly rejection e-mail her senior year. Many of the families that selective colleges target are low-income minorities who have the least experience with the college admissions process and are the most likely to be perplexed and hurt by it.

Harvard, to its credit, at least hints in its letter that its friendly gesture doesn't mean much. "There are no guarantees, nor magic formulae for admission," it says. None of the 150 other search letters I have read provides even that short disclaimer.

C.D. Mote, president of the University of Maryland-College Park, has pointed out that the more students a college rejects, the better it looks. College applicants act like hungry patrons crowding the restaurants that have the longest lines at the door. The places that are hardest to get into must be the best. But there is little research to back up that assumption, and one reason that Harvard, Stanford and Yale got about 20,000 applications each last year is that they asked for them.

Perhaps no one can stop even very selective schools from continuing to advertise themselves. The threat from competitors is too great. But a sentence or two that warns the adolescents who tear open these letters of how thin their chances are might reduce the inevitable feelings of betrayal.

It's fine to teach young people the dangers of accepting praise without considering the motives of the flatterer, but that is probably not the lesson these colleges are trying to teach.

The writer covers schools for The Post.