Unions have called the general strike a success, saying 83 percent of non-university staff and students had chosen to stay away from the classroom.

"The education sector is raising its voice again to defend a model which guarantees equality of opportunity for all," said unions in a statement released on Thursday.

The system "is under serious attack as a result of continuous cuts on educational resources" said the unions.

They called for the Spanish Government to scrap higher university fees and do away with its LOMCE reforms.

Those reforms contain unpopular measures including giving the subject of religion full academic status and subsidizing same-sex schools with government money.

The new rules also mean students will have to elect to choose between academic and technical streams — a system unions describe as elitist.

The Spanish Government argues the new reforms are necessary to fight Spain's high school drop-out rate.

The Ministry of Education also notes spending as a percentage of GDP had risen from 4.36 percent in 2007, or before the crisis, to 4.55 percent in 2013.

Thursday's strike comes a fortnight after the Organisation for Economic Cooperation and Development published study results showing Spanish adults had among the lowest results for reading comprehension and maths skills in 23 developed countries tested. 

The OECD study revealed many Spaniards struggle to understand simple charts and graphics.