Volunteers were asked to act as traffic wardens at Tilbury Pioneer Academy in Essex in September 2015.
But the BBC can reveal the powers were enforced by just one parent, with no penalty imposed.
Thurrock Council defended the project, saying it highlighted the "deterrent value of the project".
The pilot was introduced after the council said it only had six full-time traffic wardens to police illegal parking outside its 50 schools.
However, a Freedom of Information (FoI) request by the BBC showed it was halted after three months
A lone parent volunteer enforced the rules and no tickets were issued, the FoI showed.
A spokeswoman for Thurrock Council said the trial would not be rolled out across the borough.
She said: "There has been considerable improvement in parking behaviour as a result of the scheme but, due to the significant training commitment for the volunteers, continuing the project will be difficult."
Jerry Glazier, national executive member of the National Union of Teachers in Essex, said the scheme had "the right motivation, but the wrong approach".
"In the cold light of day the practicalities were such that this was simply not an effective runner," he said.
"There needs to be proper engagement with parents."
Not a single fine was issued during a £5,000 trial to get teachers and parents to police roads outside a primary school, it has emerged.