As a small, neighborhood high school opened for Upper East Side residents Monday, education activists continued to criticize the mayor for not doing enough to reduce what they say is ballooning class size at existing schools.

NY1 Education Reporter Jennifer Rainville filed this report.

A state-of-the-art high school with a rigorous curriculum and a seat for every student: it’s what Upper East Side parent Natalie Lardner says was just a dream until this year.

“I got on board as a parent activist so this school would come to fruition in time for my soon, who is 9-years-old,” Lardner said Monday.

Eleanor Roosevelt High School opened its doors this September in time for Lardner’s 15-year-old daughter Dmily to attend. On Monday, Emily, her classmates and teachers welcomed Schools Chancellor Joel Klein and elected officials to celebrate the opening of the small school, which has 239 freshmen and sophomores. The school plans to ultimately enroll 500 students in grades nine through 12.

The chancellor says he knows the school is the exception, not the rule. It's an understatement to say many city high schools are way over capacity, with some more than 1,000 students beyond what they were built for.

“Overcrowding is not a good thing,” said Klein. “Some of these mega-high schools are going to have to be reconfigured.”

But the teacher's union and some education activists say they are tired of waiting for class sizes to go down. United Federation of Teachers President Randi Weingarten, hip-hop mogul Russell Simmons and “Sex in the City” star Cynthia Nixon rallied on the steps of City Hall today, charging Mayor Michael Bloomberg's priorities are mixed up.

They criticized the mayor for fighting to keep his referendum to eliminate partisan primaries on the ballot, while knocking off a vote on whether to create a commission to study class size.

“Question 6 was struck from the ballot because Michael Bloomberg didn't think it was important enough to be there,” said Nixon.

“If kids are a priority, he needs to put it on the ballot now,” said Simmons.

But the mayor says reducing class size is better addressed through his education reforms than by revising the city charter.

“If you want to see how you get in trouble, just take a look at California. That’s what happens when you have single ballot initiatives that require spending certain percentages of the tax base,” said Bloomberg.

Simmons says he's not giving up. He and other celebrities will hit the airwaves to make sure the mayor's actions are crystal clear to voters before they go to the polls.

- Jennifer Rainville