Demand for a Catholic education is so great the WA Catholic Education Office predicts it needs to build another 30 schools in the next 13 years just to keep pace - but expansion is limited by lack of capital funding and planning restrictions.
Catholic schools are urging parents to lobby State election candidates for a commitment to more funding.
Each school has been asked to insert fact sheets about key election issues into their newsletters.
An information paper sent to schools this week predicts a 25 per cent increase in students attending Catholic schools by 2026 - the equivalent of 20 new primary schools and 10 new secondary schools.
"The projected growth of Catholic schooling will not be possible under the existing funding regime," the paper said.
The paper said every child who attended a public school because they could not get into a Catholic school would cost the Government four times as much.
Catholic Education Office director Tim McDonald called on the major parties to commit to double the funds provided under the current low interest loan scheme, which had not increased since 1995.