DOVER — The Senate passed a controversial student-testing opt-out bill Thursday, sending it on to Gov. Jack Markell.

By a 15-6 margin, House Bill 50 cleared one of the final remaining obstacles in what has been a very convoluted path.

The proposal now has passed both the House and Senate twice, after the Senate amended it last week and the House made further changes on Tuesday.

The battleground for much of the debate has been the Smarter Balanced assessment, although the field has now spread. House Bill 50 originally was focused solely on the specific standardized test, but a Senate amendment from Sen. David Sokola, D-Newark, expanded the legislation’s scope. The bill would allow parents to choose to have their children skip a state- or districtwide test.

Supporters of the legislation say assessments are given too frequently, causing undue amounts of stress for students and providing little to no benefit in return. Those on the other side counter the tests help education officials measure students and teachers.

The governor has called House Bill 50 a “bad bill,” leading to speculation he will veto it, though lawmakers have said they do not know what he ultimately will do.

On Thursday, the bill passed by a strong margin after just five minutes of discussion. Sen. Robert Marshall, D-Wilmington, was the only vote change from last week, flipping from a no to a yes.

The Senate vote was much less eventful than the House vote two days before, which saw the bill defeated before lawmakers rescinded their vote and approved the proposal, all within an hour.

An amendment from Sen. Bryan Townsend, D-Newark, that would have allowed high-school juniors to choose themselves to opt out of a statewide test was overturned through a House amendment.

Though he voted for the bill, Sen. Townsend expressed displeasure Thursday his amendment was removed.

“I think it’s interesting that we believe that high-school juniors should be able to drive on our roads and hunt with firearms and be on the brink of signing up to join our military but they’re not mature enough to decide if a test that has no bearing on their grade is something that should take,” he said.

Rep. John Kowalko, D-Newark, the bill’s sponsor, has said he believes the two Senate amendments were designed to kill the bill.

Backers have insisted the bill focuses on parents’ rights and cements an already existing right for parents to opt their children out, something school districts oppose. Education officials have warned if a large enough percentage of students chooses not to take the Smarter Balanced assessment, the state could lose millions of federal dollars.

While Gov. Markell has not stated his intentions as to what he will do, he has said he does not support the bill. If he vetoes the proposal, lawmakers would have three legislative days to overturn the veto with a two-thirds vote in each chamber.

Because the Legislature breaks for the year June 30, legislators would have to wait until January to attempt to pick up House Bill 50 again, barring a highly unlikely special session.

Parent advocates celebrated the vote Thursday, but passage is far from assured since what now happens to the bill rests with the governor.