David and Shannon Croft sued Texas Gov. Rick Perry and their school district, saying the law violated their constitutional rights because it mandated prayer, The Dallas Morning News reported Sunday.
But U.S. District Judge Barbara M.G. Lynn said the law, which offers students the option to "pray," "reflect," or "meditate" during the time, isn't equivalent to "excessive entanglement" between state and religion.
The Crofts' attorney said they are considering whether to appeal.
Civil liberties groups decried the decision, saying it is a ruling in favor of a thinly concealed attempt to reintroduce prayer in schools, the Morning News said.
But proponents of the law, including Perry, said it is simply meant to be a thoughtful moment for students at the beginning of the day.
"In an age where children are so frequently confronted with violence and disorder, 60 seconds of quiet contemplation at the beginning of each day is not too much to ask," Perry said in a statement.