The collapse of schools in Sichuan is the most politically sensitive aspect of China's May 12 earthquake, which killed at least 69,172 people and left 17,420 missing. As Beijing pledges to find out why over 7,000 classrooms were destroyed, it is bucking up against parents pressing for answers.

Below is a timeline of major events involving the Fuxin No. 2 Primary School in the town of Wufu, where around 120 students died, though no one knows the true figure.

May 12: A devastating earthquake flattens big swaths of Sichuan province. In Wufu town, the Fuxin No. 2 Primary School is a standout in the disaster, collapsing even as nearby buildings remained intact. All 32 teachers survive. Parents quickly allege their children weren't killed in a natural disaster, but in a man-made one.

May 15: Fuxin parents erect banners in Wufu alleging "human error," not the natural disaster, killed their children.

May 16: China's government pledges investigations of downed schools in Sichuan and prosecution for any wrongdoing in construction. "We cannot exclude the possibility that the construction of some buildings was of poor quality," Minister of Housing and Urban-Rural Construction Jiang Weixin tells reporters. "We will deal with this problem strictly after our investigation."

May 16: Township government gives parents of dead children 1,000 yuan (about $142).

May 19: Parents build an altar on the rubble of the collapsed school displaying photos of their children; they arrive each day at 8 a.m., the start of the school day, and stay all day. A vigil is held on the Fuxin school grounds, attended by a local government official who expresses her sorrow as a parent and pledged investigation soon. Parents remain dissatisfied.

May 25: Parents march toward the Sichuan provincial capital, Chengdu, to demand an investigation into why the school collapsed. Near Deyang City, a local Communist Party secretary, Jiang Guohua, kneels down, begging parents not to proceed. They comply. A photo of Mr. Jiang kneeling causes national sensation when it is published two days later in Chinese newspaper.

May 26: Inspectors from Chengdu and other Sichuan cities are sent to the Fuxin school.

June 1: Posters appear outside Sichuan province schools with reminder of government rules forbidding unsanctioned protests. Police roadblocks appear in Wufu, keeping outsiders from getting near Fuxin school. Local government officials go to the homes of Fuxin parents daily with requests not to visit the school, though the requests are defied. Family planning and other authorities distribute around 4,500 yuan to Fuxin parents. Parents go to nearby Mianzhu City government to request copies of Fuxin school building documents and are told the materials had been sealed and delivered earlier to government discipline authorities. Parents say Deng Ning, vice director of Deyang City Planning and Construction Bureau, has revealed to the group that the design called for a two-floor school, though Fuxin had three floors.

June 8: Parents from some Sichuan schools are warned in a letter that foreign agents, including the members of an outlawed sect called Falun Gong, are manipulating the situation to damage China's credibility and ruin the Beijing Summer Olympic Games. Letter urges them not to "lose their wits."

June 12: The government issues a letter to parents requesting more time to conduct the investigation, with a request they make no more fuss.

June 14: National teacher and education fund distributes 3,000 yuan to each parent.

June 15: Fuxin parents travel to nearby Mianzhu to listen to the vice mayor talk about a problem school there, Dongqi Middle School. Official reiterates government resolve to investigate schools, and promises parents will receive help with housing, employment and subsidies.

June 20: Fuxin parents have been told to expect findings of the investigation.