China ? Angry parents whose children were killed in an earthquake-stricken school shouted “Oh, my child!” and “Tell us something!” when police forcefully removed them Tuesday from a protest outside a courthouse.

The police action was the clearest signal yet that authorities are hardening their stance against the impromptu displays of public anger over the May 12 earthquake that collapsed schools and killed thousands of children.

The students’ deaths have become the focus for Chinese, both inside and outside the quake zone, fueling accusations about corruption in school construction. The brewing public anger has become a political challenge and threatens to turn popular sentiment against the authoritarian government as it copes with aiding millions displaced by the disaster.

Aggrieved parents and even rescuers have pointed to steel rods in broken concrete slabs that were thinner than a ball point pen among the 7,000 classrooms that were destroyed.