An East Bronx public school principal has been fined $10,000 for endorsing a Democratic candidate in a letter sent home with students the Friday before the election. The Department of Education is also investigating the school’s parent coordinator, who apparently used her city government e-mail address to solicit campaign volunteers for the same candidate, who is running for re-election to the state Senate.

As The New York Sun first reported yesterday, the principal of Public School 71, Lance Cooper, issued a letter praising City Council Member James Vacca and state Senator Jeffrey Klein. The letter encouraged parents to “endorse these Community Leaders when they need our support as a way of saying thank you for always being there for P.S. 71!”

Mr. Klein, a Democrat who represents portions of Bronx and Westchester counties, faces the Bronx Republican chairman, Joseph Savino, in today’s election. Mr. Vacca, a first-term council member, is not up for election this year.

After authenticating Mr. Cooper’s letter yesterday, education department officials consulted with the city’s Conflicts of Interest Board. The Board determined that Mr. Cooper’s letter violated the Chancellor’s Regulations, which forbids school employees from endorsing a candidate while at work, or in contact with students. Mayor Bloomberg was briefed on the matter, an education department spokesman, David Cantor, said.

In addition to the fine, which will go to the city’s general fund, Mr. Cantor said a letter would be placed in the principal’s personnel file “denoting the unacceptable action that he took.” He added that Mr. Cooper seemed “quite penitent,” and “acknowledged, as soon as we contacted him, if not earlier, that he suffered a significant lapse of judgment.”

Several messages left for the principal at his office, and for the parent coordinator on her city-paid cell phone, were not returned yesterday.

“From what I understand, Lance Cooper is a veteran and good principal, and just made a big mistake,” Mr. Cantor said. “To my knowledge, he wrote the letter out of gratitude to those officials. I think he lost his sense of judgment, and it’s going to cost him a pretty penny.”

The principal’s letter credited Mr. Klein and Mr. Vacca with helping the school secure state and city funds to outfit a science classroom, and to replace equipment that recently stolen from the school’s mobile computer laboratory.

A former teacher and school supervisor, Mr. Cooper was appointed interim acting principal in July 2001, and became principal about 14 months later. He earns $118,193 a year.

The education department has asked the school system’s special commissioner of investigation, Richard Condon, to look into an e-mail by the parent coordinator of P.S. 71, Renee Reilly. In the October 29 correspondence to an undisclosed list of recipients, she wrote that Mr. Klein, the state senator running for re-election, was “looking for volunteers on ‘Election Day’ to hand out flyers in front of PS71.” Mr. Condon was asked to determine whether Ms. Reilly had been granted permission by the principal to send the email.

Mr. Klein’s campaign manager, Taryn Duffy, yesterday denied asking Ms. Reilly to solicit Election Day volunteers. She said the senator had no prior knowledge that the letter or the e-mail would be sent.

Yesterday, Mr. Savino reiterated that he hoped political pressure did not impel Mr. Cooper to draft the letter.

Mr. Vacca’s chief of staff, Jeff Lynch, said the council member helped P.S. 71 secure funding for capital improvements, and to replace stolen computers. Mr. Lynch also said he was “taken aback” that that the council member’s name was invoked in the “poorly worded” letter.