The University of California's governing board has agreed to offer automatic places to the top 4 per cent of pupils from the state's 863 public high schools.
The 13-1 vote in favour of the new rule came shortly after California's new Democrat governor, who put education reforms at the top of his agenda, appointed several key supporters to the UC's board of regents.
University places in California will still be settled primarily by Scholastic Aptitude Test (SAT) scores. But the 4 per cent rule will make an estimated 3,600 new students eligible based solely on their performance in school, rather than an exam. About half are expected to take up their places.
The new admissions system tells pupils to "keep dreaming big dreams", said governor Gray Davis. "Keep working hard. If you really excel, you will get a place at one of the eight UC campuses."
Mr Davis had campaigned on the measure, arguing it would redress the racial balance in California's public university system after a bitterly-fought ban on affirmative action programmes saw the numbers of minority students fall.
But studies now suggest that white students from rural and poorer performing schools will be the main beneficiaries, making up 56 per cent of the new admissions, with Latinos accounting for 20 per cent, Asian Americans for 11 per cent and African Americans just 5 per cent.
What it will do, supporters insist, is inspire a "culture of academic excellence" in schools that have historically sent few students to the University of California. While they will not be guaranteed admission to such academic powerhouses as UC Berkeley and UC San Diego, places at other lesser-known but res-pectable campuses will be opened to them.
At the end of the school year, university officials will help schools compile grades for students taking college preparatory courses. Those in the top 4 per cent would be asked to take the SAT, but their admission will not hinge on its results. Private schools can join the system if they wish.
The rule is a more moderate form of a measure adopted in Texas two years ago, which admitted the top 10 per cent. Of the roughly 10,000 students in the top 4 per cent in California, 6,400 will already qualify via SAT scores.
The proposal was overwhelmingly rejected by the UC regents when it first came up for a vote last year, with conservatives arguing it would dilute the quality of students. Its approval now reflects the Democrats' new control over California and in particular education policy.