Falkirk Council says only baptised young people will be guaranteed a place at its denominational schools because they are so oversubscribed.
In a public consultation, 63% of people agreed with the plan while just 37% were against it.
The plans mean pupils who are not Catholic but live in the catchment area would have to request a place and would not be guaranteed entry.
Councils in Scotland have a legal obligation to offer Catholic education to Catholic families.
But the Scottish Secular Society (SSS) has condemned the plans, saying they amount to 'religious discrimination'.
Spencer Fildes, chairman of the SSS, told The Herald: "Falkirk Council should not be seeking to expedite religious discrimination because a child's parents have differing faiths or, indeed, no faith.
"The Scottish Secular Society implore Falkirk Council not to pursue the implementation of these measures."
A spokesman for Falkirk Council said: "The Secular Society have already written to us and their comments have been included in our Consultation Paper.
"The proposed changes are in keeping with the legislation and would, if agreed, come into effect for the 2015-16 admissions."