The classes in Rhea County violate the First Amendment's clause calling for separation of church and state, U.S. District Judge Allan Edgar wrote in his order.
County school officials "acted with both purpose and effect to endorse and advance religion in the public schools," he wrote.
"It has never been held that there is a ban on all religious activity in public schools," Edgar wrote. "For example, a student may voluntarily pray at school. Also, religious organizations may use public school facilities under some circumstances."
But the government, he wrote, "may not teach, or allow the teaching of a distinct religious viewpoint.
A couple with two children attending the schools had challenged the Bible classes. Their identities have not been disclosed. A branch of the Freedom From Religion Foundation, a nonprofit First Amendment advocacy organization, was also a plaintiff.
The 30-minute classes were held for about 800 kindergarten through fifth grade students in the county's three elementary schools. Parental consent was not required and students were allowed to participate in alternative activities if they objected to the classes.
Rhea County school Superintendent Sue Porter said she wanted a trial to show that the classes include "character education." But the plaintiffs asked the judge for a ruling before the scheduled Feb. 19 trial and Edgar granted the request.
Deep attachment to religion has gotten attention before in Dayton, a rural town about 40 miles north of Chattanooga.
School teacher John T. Scopes was prosecuted in 1925 for teaching evolution instead of creationism. The trial, known as the Scopes monkey trial, pitted two of the country's best attorneys against each other, Clarence Darrow and William Jennings Bryan. Scopes was convicted and fined $100, but his conviction was thrown out on a technicality by the Tennessee Supreme Court.
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