BRISBANE, Feb 6 - The Gap State High's uniform policy angered parents who said they couldn't afford to discard black leather shoes that were acceptable in previous years.

"It's kind of uniform policy gone mad," parent Karen Bishop told ABC radio on Tuesday, adding she did not want her daughter's education to be affected by being sent to detention.

"It's just crazy," she said.

The school's uniform policy states shoes must be leather, fully enclosed, laced and have heels of between five and 20 millimetres.

But Grace said students and parents had been warned about an enforcement over the policy the past two weeks, prior to Monday's detentions.

"It's up to the principal and school community to not only implement the uniform policy but to enforce it, and I support those principalsand the school community to ensure the policy is implemented in the proper way," Grace told reporters on Tuesday.

She said the uniform policy was formulated by the school in conjunction with the P&C and understood there had been no changes to the policy since 2004.

"I support The Gap SHS principal and the school community's actions in enforcing the uniform policy and urge all parties to take a common-sense approach and work together to resolve this issue at the school level."

Queensland Teachers Union President Kevin Bates confirmed 103 students had been sent to detention but also defended the policy. 

"The crucial thing here is that this is the school uniform policy that's been determined through consultation with the local community, with parents. It's approved by the P&C," Bates told ABC radio. 

Bates was concerned the issue had caused arguments between parents on social media and said the appropriate channel for discussion was P&C meetings.

"I think the P&C meeting next Monday night will be a lot fuller than what it usually is," he said.