WASHINGTON (Reuters) - Former U.S. Vice President Joe Biden, the front-runner for the 2020 Democratic presidential nomination, on Tuesday released an education plan aimed at boosting teacher pay and reducing the funding gap between wealthy and low-income public schools.

Biden also said he would seek to make schools safer by pressing Congress to enact a ban on assault weapons and high-capacity magazines, a proposal almost certainly to be opposed by Republicans and gun-lobby groups.

Biden detailed his proposal - his first major policy rollout as a presidential candidate - at a campaign event in Houston on Tuesday involving the American Federation of Teachers.

U.S. Senator Kamala Harris, another a Democratic candidate for president, outlined an education plan in March that would raise teacher salaries by $315 billion over the next 10 years.

Biden proposes tripling federal funding to about $50 billion annually for schools with students from low-income families, with the directive that those funds be used by districts to raise teacher pay. The federal monies would also be used to provide preschool for three- and four-year-olds and improve curricula for those schools.

The plan would seek to double the number of psychologists, guidance counselors, social workers and nurses in the public schools.

The Houston event was part of AFT’s endorsement vetting process. The union, which has 1.7 million members, is likely months away from an endorsement, as is the National Education Association, which has 3 million members.

Both unions have established a more formalized and cautious approach to endorsements than in years past, seeking greater input from rank-and-file members.

While Biden has made support from organized labor a top priority for his campaign, he may have trouble with teachers’ unions stemming from his eight years as President Barack Obama’s vice president.

The unions were highly critical of Obama’s education secretary, Arne Duncan, and school reforms the Obama administration advocated. They included tying teacher evaluation to student performance and increasing the number of charter schools nationwide.

As a U.S. senator, Biden also supported No Child Left Behind, the sweeping education-reform law advocated by Republican President George W. Bush that promoted standardized testing as a means for evaluating schools and punished those deemed underperforming. Biden later soured on the program.

A longtime gun control advocate, Biden was an author of a 1994 law that banned assault weapons and high-capacity magazines. The ban expired in 2004, and Biden has called for its renewal. He opposes arming teachers.