Mexico City, Mexico – Mexico’s Senate has shrugged off weeks of protests by teachers and overwhelmingly passed a sweeping reform of the public school system, handing President Enrique Pena Nieto an important victory in his push for a wide package of reforms intended to help boost growth in an economy that has long lagged its regional peers.

After five hours of debate, the Senate voted 102-22 in favor of a standardized system of test-based hiring and promotion that would give the government the tools to break the teachers unions’ near total control of school staffing.

That control includes the sale and inheritance of teaching jobs which has been widely blamed for much of the poor performance of Mexican schools. Mexico spends a greater share of its budget on education than any other member of the 34-nation Organization for Economic Cooperation and Development, but scores the lowest in standardized tests.

"The inheritance and sale of posts are over," Education Minister Emilio Chuayffet wrote on Twitter. "Merit is the right way to enter and grow in a teaching career."

Last week's late-night vote clears a path for Pena Nieto to move forward with a series of even more controversial reforms, including legislation that would allow private investment in the state-run oil company. But there is potential trouble ahead.

Advocates say a series of concessions to the smaller of the two main teachers unions undermined the reform’s ability to create true change in the national education system.

And despite those concessions, the smaller teachers union continued days of debilitating demonstrations in Mexico City, sending thousands of supporters to shut down the capital’s main boulevard and protest outside key government buildings. Thousands attended smaller protests in cities around the country. The union also pledged to throw its support behind a protest against the oil reform by leftist leader Andres Manuel Lopez Obrador.

The education reform initially pitted Pena Nieto against the country’s main teachers union — Latin America’s largest union and once one of the most important allies of his Institutional Revolutionary Party. The union fell into line after its head, Elba Esther Gordillo, was arrested on corruption charges in February.

A smaller union known as the National Education Workers’ Coordinating Committee (CNTE) continued protesting and eventually rallied thousands of teachers from poorer states, paralyzing large sections of the capital for more than a week. In the end, the CNTE won a number of concessions.

Reform advocates called the law an important first step but said much more remained to be done to change the system.

"It’s not everything we would have hoped for but it’s an historic change," said David Calderon, director of the education reform advocacy group Mexicans First. "Of course it’s just a change in the rules - it still has to be turned into reality."

Much of Mexico’s educational dysfunction is attributed to the relationship formed more than half a century ago between the Institutional Revolutionary Party and the teachers unions, which gained increasing control of the education system in exchange for throwing their strength behind the government in the voting box and on the streets.

Over the years, the unions developed a virtual lock on teacher hiring and promotion. New teachers must go through a union to gain a school assignment, a practice that has spawned subversive activity, including the sale and inheritance of teaching positions.

Critics say, particularly in states with schools controlled by the CNTE, union influence has transformed schools from educational institutions into mechanisms for extracting funds from the state.

Among the benefits ended by the educational reform are payments of more than $100 million a year by some estimates to thousands of teachers who work full-time as union organizers and rarely, if ever, set foot inside a classroom.

The rest of the reform focuses on reasserting government control by awarding teaching jobs to those who score the highest on a standardized test instead of funneling them through a teachers union, a measure weakened by a series of back-room compromises with the CNTE.

The constitutional reform of education was already approved in December, but teachers had hoped to block the votes on the implementation of the changes.

The dissident CNTE union, which argues that the legislation violates labor rights, is calling for a nationwide protest.