How much time do teachers spend on bureaucratic tasks?

I would argue that the time spent on bureaucratic tasks is much more than the previous answer. According to a UK-wide survey conducted in 2014, it was found that less than half the working week is actually spent in the classroom, which means while teachers are averaging almost 50 hours of work every week, they are having to manage bureaucratic tasks more often than not, which may be harming the learning experience of those they are teaching. The survey was conducted amongst "a sample of 154 schools and nearly 2,500 secondary teachers from both state and independent schools in England," and the findings are staggering. As a result of admin duties, for instance, teachers are becomming stressed and overworked, and some studies suggest that this has led to a loss of enthusiasm for the job and, consequently, more teachers leaving the profession.