TORONTO -- Ontario parents shouldn't expect a lot of feedback in the next batch of report cards. Many teachers are being told to keep it short.

The Elementary Teachers' Federation of Ontario has advised its 76,000 members to write only the bare minimum, such as a single sentence.

It's the latest move by teachers' unions to withdraw voluntary activities in protest of a controversial law that freezes wages, cuts benefits and stops strikes.

Education Minister Laurel Broten said she's asked the union to rescind its "directive," but didn't say whether ETFO president Sam Hammond has agreed to do so.

"Ontario parents deserve to know how their children are doing at school this fall, not to have their learning progress put in the middle of a dispute that doesn't involve them," she said.

Broten said she spoke to Hammond but they didn't reach an agreement over the phone. She's invited him to meet with her to discuss the matter.

She noted that the so-called fall "progress report" -- which provides more room for teacher commentary -- was launched two years ago to give parents additional information about how their children were faring in school. Little to no information puts student success at risk, she said.

Hammond wasn't available for comment, but said in a statement that ETFO's advice conforms with ministry policy, which tells teachers to use their "professional judgment" when completing progress reports.

"We've also made it very clear in our advice to members that where students are having difficulties, teachers provide more detailed information to parents through the progress report," he said in the release.

During a wage dispute in British Columbia, teachers refused to perform certain administrative tasks, such as filling out report cards, and staged a three-day walkout.

It's unclear whether teachers in Ontario will follow suit, but some have already withdrawn from other voluntary activities, such as coaching and parent-teacher meetings.

Broten said she's also asked to meet with Ken Coran, head of the Ontario Secondary School Teachers' Federation, to discuss whether they could bring back extracurricular activities in high schools as well.

Alla Poltavsky, 46, expressed frustration Thursday with the latest salvo in the labour battle between teachers and the Liberals.

"How am I supposed to find out how my child is developing by just looking at marks? That is not the feedback I want," said Poltavsky, whose seven-year-old son Victor is in Grade 2 at Toronto's Swansea Public School.

"It's an important part of their evolving in school, to know what they're doing well and what the can do better in," she added.

"They need some kind of control and commentary and analysis of their progress. A number on a page isn't going to do that."

It's "heartbreaking" and "tragic" that parents may not get the information they need about whether their child needs extra help at school, said Progressive Conservative Leader Tim Hudak.

"Parents count on that stuff," he said. "They want to know how the kids are doing."

It's "terrible advice" from the union that the vast majority of teachers will ignore, he said.

Although the Tories supported the legislation that outraged teachers, education critic Lisa MacLeod blamed the Liberals for starting a fight that's left students caught in the crossfire.

Her party made it clear to the unions from the start that they wanted an across-the-board wage freeze to fight Ontario's $14.4-billion deficit, she said.

"(The government) promised things that they couldn't deliver and that's why we're in this situation," MacLeod said.

"But at the end of the day, nobody should be taking this out on children."

The Liberals promised the "unconstitutional" law would bring peace and stability to Ontario schools, said NDP education critic Peter Tabuns.

"Instead we see turmoil in classrooms across the province," he said in a statement. "Parents and their kids are the ones who are suffering."

Rattled by the unions' declaration of war following passage of the legislation, the Liberals are trying to mend fences with the labour groups whose financial and organizational support helped get them re-elected over the past nine years.

Premier Dalton McGuinty has bought time for the Liberals to repair that relationship by proroguing the legislature earlier this week and announcing his resignation.

McGuinty said he shut down the legislature to allow for a "cooling off period" that would give them time to negotiate with unions and the opposition parties on a wage freeze for nearly 500,000 public sector workers.