As if getting a child into preschool isn’t stressful enough, parents of the under-5 set must increasingly contend with an additional headache – the “first-choice letter.”

Much like the early admissions process for colleges, a growing number of preschools ask, or gently suggest, that families send a note to their preferred school indicating a commitment to attend if they are accepted.

In a city where preschool is seen as the gateway to kindergarten and on to the Ivy League, some parents now apply to more than a dozen programs, which can cost upwards of $15,000 a year.

“The schools like to be stroked, they like to know that you really want to go there,” the founder of the Manhattan Private School Advisors, Amanda Uhry, said. She charges parents $6,000 to coach them on how to get their children into private school.

“It’s one in 11 that gets into Harvard and one in 15 into New York’s elite preschools,” she said. “There is no such thing as a safety school anymore.”

The already fierce competition to get into the premier preschools has become even fiercer in recent years with a surge in Manhattan babies.

When parents arrive at the Claremont Children’s School in the landmark former East River Savings Bank at Amsterdam Avenue and 96th Street, where perks include a computer lab for 2-year-olds, they are handed a first choice form along with the application. If applicants don’t sign, their chances of getting in could be diminished.

“We really want families who really want to be here,” the director of the school, Donna Cohen, said. Applications from parents who send in the form go to the top of the pile. When it comes to acceptance letters, regular applicants must bite their nails until March, while the applicants who indicate a commitment receive letters a month in advance.

The school receives about 300 applications for about 68 spots, but some of those seats are reserved for siblings. The letters by no means assure the candidates a spot.

While Claremont Children’s School is clear about its letter policy, parents applying to other schools are often left scratching their heads. Most preschools do not have any written rules about the letters, although there is an unspoken rule that families commit to only a single school.

Most of the city’s elite preschools are members of the Independent Schools Admissions Association of Greater New York, which indicates that letters are not required.

Cynthia Bing, the head of the school advisory service for the Parents League, tells a cautionary tale about a father whose secretary sent out six first-choice letters for him, but placed them in the wrong envelopes. The organization, which was founded in 1913 to help parents through the admissions process, advised 1,417 preschool families last year, a 27% increase over the year before.

“People have to be very careful about this,” Ms. Bing said. If schools find out that parents have sent more than one letter, they can get shut out of all their choices.

She said that in the letter parents should specify why the school is a good match for their toddler and what they liked about the program.

At the West Side Montessori School, the longtime director, Marlene Barron, tells parents not to bother sending letters, but many do not heed her advice.

“The bottom line is there are lots more kids who are applying to lots more schools, and the schools haven’t a clue as to who is really interested,” she said. “The smaller picture is that parents on their side are trying to be strategic, they are trying to figure out, ‘Where is my first choice going to matter? Did my child have a good interview or am I wasting my first choice?’ People are thinking strategically rather than just falling in love with a school, because falling in love is not enough.”

A mother of a 2-year-old on the Upper West Side said she was torn about what to do because she had already submitted a letter to her top choice. But weeks later she visited another school that she also liked.

“What are we going to do? Write a letter saying we found another school we also really like? Let’s be totally honest, that seems to guarantee that we won’t get in,” said the mother, who asked to remain anonymous because she did not want to hurt her son’s admissions chances.

In the end, she said that she wants to abide by the unspoken rules but will not retract the letter, though she is unsure whether she will stand by her commitment.

“It’s our kid’s education, so we’ll do what we think is best for him and us,” she said.

The first-choice letters have recently sparked a range of rancorous debate on some of the city’s most popular parenting Web sites.

“Did you handwrite your first-choice letter? On stationery? Nice paper? Card? Or did you type it up?” one parent posted on Urbanbaby.com.

Another parent posted a query asking about sending an “I love you” letter, a lesser form of the first-choice letter that carries with it no commitment.