Na Kyung-won Photo: IC

A scandal over educational privilege in South Korea that threatened to derail the new justice minister's appointment has spread to engulf the opposition's parliamentary leader, whose son is a student at Yale.

The world's 11th largest economy is an intensely competitive society where teenage students are under tremendous pressure to win admission into elite universities.

Success can lead to lifelong advantages in employment, society and even marriage, and any hint of manipulation of the process by wealthy or influential parents outrages ordinary South Koreans.

Prosecutors in Seoul said Wednesday they had opened a probe into allegations that Na Kyung-won, the parliamentary floor leader of the opposition Liberty Korea party, pressured a Seoul National University professor to accept her son as an intern.

The teenager was later named the lead author of a medical paper that won him first prize in a US scientific competition - "Research on the Feasibility of Cardiac Output Estimation Using Photoplethysmogram and Ballistocardiogram" - and he ­subsequently secured a place at Yale to study chemistry.

But his supervisor Yoon Hyung-jin told broadcaster KBS that the paper was "beyond the level that a high-schooler could have comprehended."

"It's clear he had not ­understood what he was doing," he said. "But we gave him ideas."