The longest legislative session in state history may soon be over.

Republican and Democratic leaders in the state Senate announced Wednesday they have agreed to a two-year delay of a requirement that high school students pass a biology exam to graduate.

That deal clears the way for the Senate to vote to suspend Initiative 1351, which requires smaller class sizes in all elementary and secondary grades. The House has already voted to suspend the measure for four years.

Suspending the initiative requires a two-thirds majority. On July 1, Senate Democrats withheld the votes needed to reach that mark because they wanted a bill reforming the high school assessment system also to be voted on.

Not suspending the initiative opened up a $2 billion hole in the new state budget.

Resolving the dispute on the high school testing has been the focus of Senate leaders the past week.

Senate Republicans, who hold the majority, had refused to consider a House bill to eliminate the biology test requirement completely. A bill introduced Wednesday will delay the end-of-course biology test requirement for the classes of 2015 and 2016.

This will ensure that as many as 2,000 students who did not pass the biology test will still be able to get their diplomas this year.

Senators are expected on the floor at 2 p.m. Thursday. The House, which also must pass the testing reform bill, is expected in on Friday, which will be the 176th day the Legislature has been in session this year.

Here’s the statement issued by Senate leaders Wednesday:

This morning the state Senate’s Majority Coalition Caucus and Senate Democratic Caucus reached an agreement regarding a two-year suspension of the state’s end-of-course biology graduation requirements.

The agreement sets the stage for the Senate to address the delay in Initiative 1351 as passed by the House of Representatives.

The Senate will convene Thursday afternoon, July 9 with the expectation of acting on these and any other bills necessary to complete its work.