The Maryland Senate approved legislation Thursday that would slowly allow more children into some pre-kindergarten classes, which is seen as a small step toward a much more ambitious goal of allowing all four-year-olds to attend for free.

Senators voted 44 to zero to approve the legislation, which now awaits action by the Maryland House of Delegates.

Right now, Maryland public school systems are required to offer pre-kindergarten to economically disadvantaged or homeless 4-year-olds. To qualify, the child’s family must make less than 185 percent of the federal government’s definition of poverty. For a single parent, that would mean making about $28,693 or less. For a family of four, about $43,567 or less. During the 2012-13 school year, more than 26,400 4-year-olds were enrolled.

The legislation, which was sponsored by Gov. Martin O’Malley’s (D) administration, would provide grants to local school systems and pre-kindergarten providers that want to accept children from families making 300 percent of the poverty rate. For a single parent, that would mean making up to $46,530. For a family of four, up to $70,650. Providers could also apply to expand some half-day programs to full day and, in some cases, offer care for up to 12 hours a day at designated centers.

State officials hope that the funding will help an additional 1,600 children across the state. O’Malley has already set aside $4.3 million in next year’s $39 billion budget to cover the cost of this small expansion.

Pre-K has been a hotly contested issue for the three leading Democratic candidates for governor, even though they all support some form of expanding pre-K classes to even more students.

One of those candidates, Lt. Gov. Anthony G. Brown (D), praised the Senate vote in a statement on Thursday and said that it “represents the first step toward expanding pre-kindergarten to all Maryland children.” One of Brown’s goals is to provide voluntary pre-K classes to all Maryland four-year-olds, regardless of income. That would cost at least $120 million per year, Brown has said, and would be paid for by proceeds from Maryland’s gambling revenues.

Del. Heather R. Mizeur (D-Montgomery), who also is seeking to become the state’s next governor, has proposed phasing in full-day pre-K programs for all 4-year-olds and half-day programs for 3-year-olds from lower-income families. The cost of the initiative, once fully implemented, would be close to $280 million a year. She suggests that Maryland legalize marijuana and use the tax revenue it generates to fund pre-kindergarten education.

And Attorney General Douglas F. Gansler (D) has pledged to expand the state’s pre-kindergarten offerings from half-day to full-day programs and increase the eligibility requirement to 300 percent of the poverty definition. He says such an expansion would cost about $20 million a year and would be funded with gambling proceeds budgeted from the horse-racing industry.

Brown has attacked Gansler’s plan as not helping enough children, while Gansler has called Brown’s plan unaffordable. Mizeur has said neither of her opponents’ plans go far enough.