Headteacher Phil Birch will later this month launch a campaign to raise an initial £20,000 in donations from the community at the school's special 50th anniversary open day.
And staff, parents and students are expected to learn whether Lancashire County Council will support their proposal by December this year.
Mr Birch said: "The kids love their sports, but when it's raining, it's a real challenge for us. We're one of only a few schools in Lancashire that does not have a sports hall and we have put forward an 'urgent case' to LCC."
The need for a sports hall at the school was first identified by Ofsted in 1999, but despite numerous site visits from the LEA, no funding has ever been granted.
Mr Birch hopes that by raising a proportion of money themselves, the school will be able to prove that there is a real need for an improvement in facilities.
He continued: "If we do nothing, then nothing will happen.
"We are hoping that our drive to raise money will persuade them that this matters for our community as well as for the high school."
The school's open day will take place on October 11, when Mr Birch will explain the plans to the public. It is hoped that supporters will be able to 'buy a brick' as part of the sports hall appeal.
Mr Birch added: "As headteacher, I believe the school needs quality facilities to give the children the quality learning experience they deserve. We are mindful that the Olympics will be held in London in 2012 and we want to give all young people opportunities to develop their sporting talents."
The school's proposals co-incide with a call for an all-weather pitch in the town by Garstang Ladies Hockey Club coach Dave Gee, and a second phase of the school's 'strategic plan' could include an artificial outdoor surface, to be built alongside the new hall.
Following a £7,000 grant given to the hockey Club by the Big Lottery Fund, Mr Gee said he hoped the success of the club would put pressure on funding for all-weather facilities.
He said: "Garstang has football teams, cricket teams and hockey teams and they all have to go to Preston to use all-weather facilities. It's quite amazing really.
"We will be pushing to raise the funds to build an all-weather pitch, and the high school would be the perfect place for it."
Chairman of Garstang Cricket Club, Charlie Collinson, added that he would also support plans for an artificial pitch.
He said: "It would be a tremendous advantage, not just from a cricket point of view but for everyone in Garstang and the surrounding area.
"It is something Garstang has needed for some time and is a facility that I'm sure could be utilised by many clubs and organisations.''
Mark Armstrong, treasurer of Garstang Football Club, added that an artificial pitch with flood lights would be fantastic for the town.
He said: "We currently use the facilities at the University of Cumbria in Lancaster and previously we have had to use Preston Sports Arena. We struggle to find somewhere to train every season. It would be something we would look to get involved with definitely."