A booth in 2010 Reuters

(Reuters) -- Democratic candidates backed by wealthy advocates for charter schools squeaked past rivals backed by teachers unions in two California state assembly primary races on Tuesday, highlighting a bitter split in the Democratic Party over education policy.

The most contentious race was in Assembly District 46, a heavily Democratic swath of Los Angeles suburbs.

Wealthy philanthropists, hedge-fund managers and internet entrepreneurs -- bound together by a common goal of overhauling public education -- spent an eye-popping $1.4 million to bolster the candidacy of Brian Johnson, a Democrat who until recently ran a network of charter schools.

Johnson narrowly edged Andrew Lachman, a Democrat supported by the California Teachers Association, to secure second place in the six-person primary and earn a chance to face voters again in the fall, according to final results from the California Secretary of State's office.

Under California's new non-partisan primary system, the top two finishers advance to the November general election regardless of party affiliation.

The teachers union spent nearly $500,000 on ads attacking Johnson, but he drew 20.3 percent of the vote, to Lachman's 19.3 percent. The top vote-getter was another Democrat, Adrin Nazarian, the chief of staff to a Los Angeles city councilman. Nazarian has been endorsed by several other unions and college faculty associations.

A similar pattern played out in Assembly District 57, which runs along the border between Los Angeles and Orange Counties in Southern California.

Democrat Ian Calderon - the son of one of the most powerful state assemblymen in the capital Sacramento - beat out fellow Democrat Rudy Bermudez by 231 votes in Tuesday's primary to advance to the general election. Bermudez, a former parole guard, was endorsed by the California Teachers Association, though the union did not spend money on the race.

The top vote-getter was Republican businessman Noel Jaimes, but the district is overwhelmingly Democratic, making Calderon the favorite for November.

Calderon, a 26-year-old surfing champion and newcomer to politics, has pledged to give parents unprecedented power over their public schools, including the right to fire failing administrators, direct extra pay to successful teachers and control budgets.

That agenda resonates with a coalition known as education reformers, who have been working in California and nationally to promote a more free-market approach to public education. Teachers unions bitterly object, saying there's no proof the reform agenda will improve student learning.

Among the policies opposed by teachers unions: Expanding charter schools, which are publicly funded but typically run by private firms; evaluating teachers in large part by their students' scores on standardized tests; and abolishing the seniority rules that protect veteran teachers from layoffs.

Teachers unions have long been among the most reliable -- and most generous -- allies of Democratic politicians. So the education reform community has moved aggressively to provide an alternative.

Donors such as developer Eli Broad, Netflix CEO Reed Hastings and Laurene Powell Jobs, the widow of Apple co-founder Steve Jobs, have spent heavily to back Democratic politicians willing to buck the teachers unions.

Michelle Rhee, the former chancellor of the Washington D.C. public schools, also emerged as a major player in the California primaries.

Rhee runs an education advocacy group, StudentsFirst, which spent $370,000 to back Calderon and about $400,000 in support of Johnson. The political action committee she founded to engage in California races started out with $2 million, which would leave more than $1 million in reserve for the general election.

(Reporting by Stephanie Simon in Denver; Editing by Paul Simao)