A fragile private-school student and his dad are suing the city Department of Education for a retest after he bombed a high-school entrance exam because rowdy pupils broke his concentration, according to court records.

Barry Tessler, 12, had his heart set on attending elite Staten Island Tech. He spent his summer studying and taking a Kaplan course to prepare for the test.

But on Oct. 27, Tessler left the examination hall at New Dorp HS in tears because other test takers distracted him and he was unable to finish.

“Several test takers that were sitting near me spoke loudly, laughed, giggled and sang,” according to Tessler’s written statement.

Tessler said he complained to the proctor, but she was unable to control the children.

Tessler and his father, Akiva Tessler, an administrative judge with the State Liquor Authority, protested to school and DOE officials, but got nowhere.

So last week, they sued in Manhattan Supreme Court, demanding that Barry be allowed to complete the test or retake it.