A Denver judge blocked Colorado's first school voucher program Friday, calling the program to give parents in the state's wealthiest county checks for tuition at religious schools a "substantial disservice to the public interest."

Denver District Judge Michael Martinez sided with a group of parents, the American Civil Liberties Union of Colorado and the group Americans United for Separation of Church and State. They asked for an injunction blocking the "Choice Scholarship Pilot Program" in Douglas County.

The voucher opponents argued the program violates the separation of church and state because it gives taxpayer money to parents for use at approved private schools, including some religious schools.

The judge noted that some of the schools authorized for Douglas vouchers require students to attend religious services. Martinez said the voucher program "violates both financial and religious provisions set forth in the Colorado constitution."

School-choice advocates vowed to appeal. More than 200 students have already gotten voucher money from the county to use this fall. One of the private schools in the program starts Monday, and it wasn't immediately clear whether any of the checks had been cashed. A message for the school district spokesman was not immediately returned Friday afternoon.

The U.S. Supreme Court has given its backing to voucher programs, ruling they don't violate the U.S. Constitution. But courts in several states have overturned voucher laws because they went further toward supporting religious institutions than their state constitutions allowed.

A new voucher program covering the entire state of Indiana is similar to the one in Colorado and is under legal challenge that state. An Indianapolis judge has said he'll decide next week whether to issue an injunction in that state.

A spokeswoman for the ACLU of Colorado said the plaintiffs in the Douglas case don't oppose religious schools, but objected to taxpayer money being used.

Douglas County officials argued that because the scholarship checks went to parents, who would then choose their child's school, the county wasn't improperly sponsoring religion. Plaintiffs insisted the parent pass-through was a ploy to get around the constitution.

"The court correctly recognized that it's unconstitutional for the state to subsidize the religious education of a child," ACLU spokeswoman Rosemary Harris Lytle said.

A lawyer for parents expecting vouchers said they were distraught by the ruling but hoping for a quick reversal.

"We'll be moving as quickly as possible to try to get this program back in place for this school year," said Michael Bindas of the school-choice group Institute For Justice.

Douglas school officials approved the voucher program last spring, and some parents have already gotten scholarship checks. Hundreds more are on a waiting list.

One of the parents testified near tears last week at the injunction hearing that her son has a form of autism and she wouldn't be able to send her son to the proper school without the voucher money.

Highlands Ranch mom Diana Oakley said her son can't get the necessary education at the county schools.

"Inside those four walls, he doesn't fit," Oakley said.

Martinez conceded that voucher recipients would be hurt by the injunction, which he said "will undoubtedly result in significant hardships for the families already selected." But Martinez concluded that constitutional concerns outweigh the hardships and that it was "clear and certain" plaintiffs would prevail in their legal challenge.

"The threatened constitutional injuries to plaintiffs, and the other residents of Douglas County they represent, outweighs the threatened harm" to families expecting vouchers, Martinez wrote.

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Read the injunction: http://goo.gl/A82zh