Supporters have billed it as the most important piece of legislation to emerge this year from the D.C. Council — bigger than raising the minimum wage to $11.50 and decriminalizing marijuana, and far more significant than voting to rename the Redskins.

A bill expected to clear its first hurdle Wednesday — and that a supermajority of council members have signed on to support — would provide a vast swath of the city’s poorest students with as much as $60,000 each to attend college.

In a city that spends more than $18,000 in tax dollars per student annually but only graduates six in 10 from high school on time, it’s the next big idea to fix the District’s broken education system, argues council member David A. Catania (I-At Large).

“This is about leveraging the considerable investment we have made in pre-K through 12th grade,” said Catania, chairman of the council’s education committee and the measure’s principal author. “This is about investing in homegrown human capital, not the least of which, at this point, is the notion that if you are from here, this city will make a promise to you to help you achieve your educational goals.”

How the city will pay for a program that Catania has estimated could cost as much as $50 million a year remains an open question. So, too, does the issue of whether Catania — who persuaded nine other council members to co-introduce the bill this fall — will be able to hold that majority together after announcing that he is exploring a run for mayor.

The legislation, which at first seemed jaw-dropping for its price tag, has taken shape in hearings packed with D.C. public high school students who sometimes cheered in support.

Under the latest version of the bill, which the education committee is scheduled to vote on Wednesday, the city’s public school students would benefit on a sliding scale from the new grants, which Catania has dubbed D.C. Promise.

Students from families of four whose parents earn up to $54,000 would receive the largest grants, but middle-income families also would benefit. The same size family with income of up to $215,000 annually would still be eligible for up to $15,000 toward the cost of a bachelor’s degree.

Promise money would become available to students only after they exhaust all other possible grant assistance, including federal Pell grants and the D.C. Tuition Assistance Grant program.

D.C. students’ highly prized TAG subsidy provides up to $10,000 a year to defray the cost of attending an out-of-state public university and up to $2,500 a year to attend a private university in the Washington area or a historically black college.

If there is a hitch in Catania’s plan among his council colleagues, it is whether Congress could decide to end the federally funded TAG program if it sees that the District can afford to cover the hefty Promise grants by itself.

“If the Promise Act looks like it will reduce the federal dollars, then I think we need to look closely at the costs and benefits,” said D.C. Council Chairman Phil Mendelson (D), who is among those who co-introduced the bill. Mendelson said this week that his vote ultimately would depend on an answer about the federal TAG funding.

Council member Tommy Wells (D-Ward 6), a member of the education committee, said he would vote for the bill. But he wants assurances, before the full council votes on the issue, that the Promise plan doesn’t “jeopardize federal dollars” for TAG.

Catania has pitched the proposal as a way to address inequality in the District, where more than half of adults hold a bachelor’s degree, according to census data, but more than one-third are functionally illiterate, according to a 2007 study.

More students would go to and finish college if they could envision paying for it without accumulating huge debt, Catania argues. Students who win the maximum Promise award could put a significant dent in the amount of loans they have to take out: D.C. residents carry an average student debt of $41,200, according to the Federal Reserve Bank of New York.

In 2011-12, the average price of a four-year public college, including tuition, books, room and board, was $17,900, according to the National Center for Education Statistics. Private non-profit schools averaged $34,400.

The original bill has been revised, and it now extends the grants to graduates of D.C. private schools and home-schooled students in addition to those who attend D.C.’s traditional public schools and public charter schools. Eligible recipients must have attended a D.C. school from grades nine through 12 and must live in the city when they apply.

Grants would be doled out on a sliding scale, with the largest amounts reserved for the poorest children. Students from families of four that have a household income of $53,650 — half of the city’s annual median household income — would be eligible for the maximum award of $12,000 per year.

The smallest award -- $3,000 per year – would go to families earning between 126 percent and 200 percent of the city’s annual median income, or about $215,000 for a family of four.

Students could use the money at any post-secondary institution across the country, including for career and technical education.

The District would not be the first to offer substantial college financial aid to its students in an effort to keep families in the city and boost graduation rates. Such “promise” programs – some funded publicly and others privately — have sprung up in more than two dozen U.S. cities, including Kalamazoo, Mich., Pittsburgh, Syracuse, N.Y., and El Dorado, Ark.

Some states also sponsor scholarship programs, many of them merit-based. Low-income middle-schoolers in Washington State, for example, can qualify for a state-funded scholarship program that will cover their tuition at many public and private colleges in the state, as long as they aren’t convicted of a felony and maintain a high school grade-point average of at least 2.0.

Seventy-eight percent of middle-schoolers who enrolled in the Washington State scholarship program graduated from high school, compared with a statewide graduation rate of 59 percent for those who did not take part in the program, according to Bob Craves, who helped administer the Washington program as an executive of the College Success Foundation.