In what is likely to be an emotional event, hundreds of parents are expected to pack into a Harlem church tonight to learn if their children have won one of the coveted slots at the new Harlem Success Charter School.

More than 440 parents have applied for 155 spots in the school, which is set to open in the fall.

“Winning a lottery in this case is not winning millions of dollars but the chance for your child to receive an excellent education,” the head of the school, Eva Moskowitz, said.

The former City Council member served as the chairwoman of the Education Committee until this year. After making an unsuccessful bid to be elected president of Manhattan, she took a post at the school.

Harlem Success is one of 12 new charter schools to open in September.

Operated as independent public schools with their own boards of directors, charter schools are given five-year charters that can be revoked by the state if academic goals are not met. They are not required to hire union teachers or follow citywide curriculum.

When the state approved the creation of charter schools in 1998, the law limited the number of such schools to 100. In New York City, about 12,000 students attend 47 charter schools.

The state has now reached its cap and Albany is hashing out whether to expand the number of charters granted. Ms. Moskowitz said she hopes tonight’s event will send a message to state legislators.

Opponents of charter schools say they siphon off much-needed funds from regular public schools.

Seth Andrew, the director of another charter school to open in Harlem in September, Democracy Prep, said he will not be inviting the public to watch the school’s lottery next week.

“There are going to be three times as many parents that are going to be sad than happy,” Mr. Andrew said. He will offer parents who are put on the waitlist the names of charter schools with available slots. He also plans to give them a postcard they can send to Albany asking legislators to raise the cap.