Nursery schools across Germany remained closed today, as childcare staff went on strike over pay and work conditions, according to dpa. Around 11,000 educators didn't go to work, according to Verdi trade union, forcing thousands of parents to find alternative arrangements for their young children. The strikes affected the states of North Rhine-Westphalia, Rhineland-Palatinate, Hessen, Bremen, Schleswig-Holstein, Saarland and Baden-Wuerttemberg. The industrial action was to be extended to other states such as Bavaria and Lower Saxony on Monday, Verdi trade union leader Frank Bsirske said at a rally in Cologne. "High work intensity and little personnel define everyday life in childcare centres," Bsirske said, adding, "The physical and emotional pressure is high." The trade unionist said educators were often confronted with noise levels exceeding 100 decibels. "That corresponds to the levels of a jet plane," Bsirke added. He said carers often suffered muscular and skeletal problems resulting from lifting children. The federal and regional governments have set ambitious aims for pre-school nurseries to teach children basic skills, after Germany ranked poorly in the so-called PISA worldwide test of children's school performance run by the Organisation for Economic Cooperation and Development (OECD). As a result, politicians are calling for nursery schools to provide early learning schemes for children of pre-school age, although many nurseries lack staff and money, and educators say they are often not trained sufficiently. By 2013, Germany is also to increase the number of childcare places, so they are available for more than a third of all children younger than three. Family Minister Ursula von der Leyen expressed sympathy for childcare staff. "The increase of childcare provision must be accompanied by an improvement in quality," the minister said. "Of course, that costs money," she added in an an interview with daily Ruhr Nachrichten. In the city of Ulm, where most childcare centres remained shut, mayor Ivo Goenner showed little sympathy. "The working conditions of the educators are far from inhuman," Goenner said. Reduced tax revenues meant cities and communes could not spend more money on childcare, Goenner added. Roughly 2.25 million German children attend nursery schools and daycare centres. School is compulsory in Germany from the age of 6.