In February 2011, Nicole Smolowitz’s son was admitted to the Mandell School on the Upper West Side. She signed a contract and paid the $7,500 deposit.


By late April, the family’s financial situation had changed, and private school was no longer an option. Ms. Smolowitz called the school to say her son would not be able to attend. She did not expect to get her deposit back — but she was told she had to pay the remaining $26,250, as well.


“It’s April,” she said she told them. “I will find someone for you to take my child’s spot.” The school told her that was not how things were done. Then, in September, Mandell sued.


For most parents, getting their child into a private school is a moment of joy, or at least relief. But uncomfortable conversations take place at this time of year, as some parents reconsider.


Sometimes these conversations lead to an amicable parting. Other times, they lead to a bare-knuckled fight in court.


Since 2009, at least five private schools in New York City — Mandell, York Preparatory School, Friends Seminary, Léman Manhattan Preparatory School and the Little Red School House and Elisabeth Irwin High School — have sued parents for tuition.


The schools’ argument is simple: Parents sign a contract when they accept placement, saying they will send their child to the school the next year and pay the agreed-upon price.


Parent-oriented Web sites like UrbanBaby.com are now filled with anxious questions about how far schools will go to enforce those contracts.


The contractual deadline at which a family is on the hook for a year’s tuition varies: at Mandell, it is in March; at Riverdale Country School, it is May 31; and at the Trinity School, it is in July. If parents withdraw their children before the deadline, they lose only their deposit, usually several thousand dollars. Typically, parents must sign a new contract each school year.


While financial strain is an oft-cited reason for parents withdrawing their children from private schools, another factor is the availability of public gifted-and-talented programs. Often, the deadline for parents to commit to a private school comes before the city’s Education Department sends acceptance letters for the gifted programs, which it is expected to do this year in late May.


Lawsuits are not the only tool available to schools: some parents have reported being threatened with debt collectors, leading many to cave and pay for an education their child will not receive. And defending a lawsuit is often not financially worthwhile, as the cost of a lawyer can approach the amount the school is demanding.


Frances Langbecker said she was shocked when Friends Seminary sued her after her daughter had been there for six years, especially because she had been a class parent and an active fund-raiser for most of that time.


In 2008, Ms. Langbecker was working in real estate, and her husband was starting a company. Because of the financial crisis, she had her daughter, Isabella, apply to New Explorations Into Science, Technology and Math, or NEST+m, a selective public school on the Lower East Side. When Isabella was accepted days after Friends’s back-out deadline, she said, she called Friends to say that while she did not think Isabella would attend NEST+m, they planned to go to the orientation to check it out.


According to Ms. Langbecker, while she and her husband were still deciding where to send Isabella, the principal of Friends sent Isabella a letter saying he was sorry to see her go.


Then Friends sued for $28,700. According to the school’s court filings, the Langbeckers had withdrawn Isabella after the back-out date. “It was ugly, bad, devastating,” Ms. Langbecker said. “The Friends community was my community.”


In their own court papers, the Langbeckers said Friends had let other parents back out and questioned whether the lawsuit fit with the school’s Quaker principles. They also said the school had not kept up its end of the contract because it had failed to deliver a quality education at times, like when certain math and English teachers were out. Ultimately, Ms. Langbecker said, both sides dropped the case. David Black, the lawyer for Friends, did not return calls for comment.


While doing research for the suit, Ms. Langbecker came upon another case that gave her hope: the Gunderson case, as families who have been sued call it.