The State Opposition has promised $54 million for a new high school in Ellenbrook if it wins the March election.

Labor leader Mark McGowan says the North Ellenbrook Secondary College will be operational by 2015, and cater for the growing population in Perth's north-east.

The new school would cater for Years 7 through 12, and would ease pressure on the Ellenbrook Secondary College which has increased its student population from 550 in 2008 to almost 1,300 last year.

Labor says at least 26,000 people now live in and around Ellenbrook and providing educational facilities for the areas residents should be a major government priority.

Mr McGown says the school is needed to keep up with increasing demand.

"The current high school now has more than 1,200 students at it," he said.

"A few years ago it was at 500 students so you can see the growth in population.

"This is an area where 50 babies a month are being born, it is a massively growing area."

Ellenbrook falls within the marginal seat of West Swan, which Labor holds by a margin of 4.1 per cent.

Mr McGowan says he is confident of the sitting MP Rita Saffioti's chances, as well as the party's candidate in the neighbouring seat of Swan Hills, Ian Radisich.

However, the Treasurer, Troy Buswell, has dismissed Labor's promise to build the new high school, saying the government has already committed to the project.

"The school that was announced today in Ellenbrook was already announced by the Government at the time of the last budget," he said.

"So if the sum total of your election commitments is to run around the countryside announcing things that are already in the budget, well then good luck."