Tower Hill School in Farnborough currently has 249 children on its roll but has capacity for another 80.
Staff believe the decline in the number of military families living locally and a mixed Ofsted report are key reasons for the shortfall.
But while teachers and governors say youngsters can benefit from smaller class sizes, they are launching a publicity campaign to sell the school to the local community.
Headteacher Mark Dunbavand, pictured outside the school, said: "If the Army aren't going to replace their personnel we want everyone else to know that we are here."
The school, which dates back to the 1920s, serves the area west of Farnborough Road and south of the main railway line.
It is almost hidden on land off Cody Road and Fowler Road, with no main access from a major road or street.
A significant proportion of its pupil roll used to come from military families living in the area.
But the ratio dwindled when soldiers and Ministry of Defence workers moved away and were not replaced.
Inspectors criticised the leadership of Tower Hill after a visit two years ago, although they agreed that it was still an effective school.
Ofsted, the education watchdog, found that an acting headteacher was only in school for a few days each week and that the governing body "had not established itself as a critical friend to the school".
The body also criticised the narrow learning opportunities for children.
But Mr Dunbavand, who has been in his post since January last year, insists things have been turned around.
"The problem is that we are not very high profile. In the past the profile of the school hasn't been as positive as it could have been in the area and people don't realise it has changed," he said.
"Although they could be within half a mile of the school, people may not even know that we are here or only remember how the school was four or five years ago.
"We are far more forward-thinking and positive but we don't get the credit for that and we don't get the children because of that."
Tower Hill now has a full complement of teaching staff and is implementing an improvement plan to take the school forward.