TORONTO -- Hundreds of thousands of elementary school students in two of Ontario's largest boards will not be receiving report cards as an administrative strike by teachers hits the one-month mark.

The Elementary Teachers' Federation of Ontario has been on a work-to-rule campaign since May 11 to protest what it calls unreasonable demands from school boards and the province at the central bargaining table.

They say teachers are transmitting marks to principals, but the school boards say it's being left to principals to input the marks -- which some say is too mammoth a task.

The Toronto District School Board says the production of report cards for more than 170,000 students can't be done without that step by the teachers, so parents will instead get letters confirming their child's placement for the upcoming year.

The Peel District School Board will also be issuing placement letters for its 112,000 elementary students, saying it's "impossible" for 350 principals and vice-principals to do the work of nearly 5,000 teachers.

Education Minister Liz Sandals says she understands it will be more difficult for larger schools and boards to produce full report cards during the job action and that some may only be able to send letters of promotion.