The Somerville Board of Aldermen passed a resolution Thursday night opposing the establishment of the Somerville Progressive Charter School.

The charter school "is going to have, I think, a disastrous effect on the city's finances," said Alderman At-Large William White.

The Somerville Public Schools administration, the Somerville School Committee and the mayor, among others, fear the proposed charter school would take money away from the public school system. The resolution passed Thursday says, "[A]pproximately $4.78 million per year would be deducted from the City's budget."

On Thursday, an organization called the Massachusetts Charter Public Schools Association announced that it filed a complaint against the Somerville School Department, in doing so disagreeing with those numbers.

"The state would provide the city with millions of dollars in additional state aid for hosting a charter public school," the organization's announcement reads. "Over the first five years of the school’s operation, the City would receive approximately $7.5 million in additional aid from the state."

Alderman At-Large Dennis Sullivan, however, said the proposed charter school would have a "devastating impact" on Somerville's finances, and he said, "I think the financial impact it will have on the system is relevant."

"I think it would be devastating if another charter school comes in here," said Ward 1 Alderman William Roche.

The aldermen discussed a desire to draft in the future a more formal document opposing the charter school based on legal grounds.

A public hearing on the charter school is planned for Dec. 14.