Gangs of high school students hurled stones and fire bombs at police stations in Athens suburbs on Thursday, in a sixth day of anti-government violence since the police shooting of a teenager. Central Athens was calmer than in previous days as people returned to work after a 24-hour general strike on Wednesday called by unions opposed to pension reforms and privatization. Trouble flared before dawn in Athens when students occupying the university clashed with police. By mid-morning, it spread to 15 police stations, from upmarket neighborhoods of north Athens to the working-class south. Data released on Thursday showed that economic hardship is hitting more Greeks. Unemployment, especially high among young people and women, rose to 7.4 percent in September from 7.1 in August, reversing four years of decline, and economists said it would keep climbing as the global crisis reached Greece. Many students carried banners reading “Why?” in reference to the police killing of 15-year-old Alexandros Grigoropoulos on Saturday, which ignited public anger at police brutality and economic difficulties aggravated by the global downturn. Around 500 people besieged the central police station in the northern city of Thessaloniki, while crowds gathered in the western port of Patras and the northern city of Ioannina. A left-wing rally was due later in central Athens, more protests were announced for Friday and Monday, and many Greeks asked how much longer the government could remain in power. “The government has shown it cannot handle this. If police start imposing the law everyone will say the military junta is back,” said Yannis Kalaitzakis, 49, an electrician. “The government is stuck between a rock and a hard place.”