The Education Department of Brazil's biggest city says more than 90 percent of the public schools it runs have been affected by a weeklong strike by teachers protesting proposed changes to their pension plans.

The department says that teachers at 93 percent of the 1,550 schools administered by the Sao Paulo city government are on strike. Another 1,500 privately run public schools haven't been affected by the strike.

The number of teachers on strike and the number of students affected by the stoppage was not immediately available.

The city is considering increasing civil servants' monthly pension contributions from 11 percent to at least 14 percent.