In addition to the new Social Insurance Law, they are adjusting the income tax rates. I'll post a new topic about that so the information can be easily found in the future. The new income tax rates take effect September 1. In fact, most people will see a reduction in income tax due, but probably not enough to offset the new social insurance tax.
Just to answer dragonsaver's post above, the tax on 8450 will go from 422.5 (the actual tax that's payable on 8450, someone at your school is pocketing the other 27.5) to 260. So they'll save 162.5 in taxes not taking into account the Social Insurance tax which, as I understand it, will vary by region and city.