At least 25,000 Croatians demonstrated in the main square of the capital Zagreb on Wednesday accusing the government of political meddling in an education reform meant to help improve the country's weak
Smaller protests by civic groups and teachers unions took place in 12 other Croatian cities, organizers said.
The protests, held under the slogan "Croatia can do better", came after an expert group organizing the reform withdrew from the project, complaining that the new center-right government was interfering too much in the planning.
The experts were appointed 16 months ago by the previous center-left government and wanted to modernize schools to give students more marketable skills. Local businesses complain that graduates are unprepared for the labor market.
The experts did not detail the alleged interference, but it appeared a staunchly conservative group in the government wanted its views reflected in teaching materials about controversial social issues.
The protest is a blow to an already fragile government that might collapse after fewer than five months due to a row within the coalition over an alleged conflict of interest involving Deputy Prime Minister Tomislav Karamarko.
A no-confidence vote on Karamarko, who is head of the conservative HDZ, the biggest party in the ruling coalition, must take place before June 18.
Croatia has a jobless rate of almost 16 percent and has just started to recover after six recession years from 2009 to 2014.