Kent County Council (KCC) is expected to put up its Young Persons' Travel Pass from £200 to £250 in September - a year after the price doubled from £100.
"We have just set up an e-petition and we will be emailing all the schools and hoping people will sign," said Staplehurst campaigner Katya Thornton.
KCC said it could not provide a cheaper pass because of government cuts.
The travel pass gives unlimited access to Kent's buses for 11 to 16 year-olds on weekdays between 06:00 and 19:00 from the start of the academic year until 31 July.
"Some people will say the increase is only £50 but that's a 25% rise and its coming on top of last year's rise," said Ms Thornton.
"For some people like me this has a real impact.
"It's very unfair for those of us who live in rural communities because I don't have the right kinds of schools on the doorstep.
"I would prefer to send my children to a school five of 10 minutes away where they could walk but I can't do that."
Leader of the UKIP opposition on the council Roger Latchford, said he was appalled at the increase and would oppose it when it was debated by the council's cabinet on Monday.
Tory-run KCC said buying a bus card directly from the operator could cost more than £800 a year.
It said government cuts meant the council had to save £209m over the next three years and subsidising bus passes currently cost the council about £15m a year.
"It is a discretionary scheme - we don't have to do it," said Conservative Matthew Balfour.
"Our subsidy is being reduced but that still leaves a cost to the taxpayer of £338 per pass."

The AU has already said it is investigating allegations that its soldiers have been involved in killing civilians in the town in July.
But this is the first detailed account of this alleged incident.
Witnesses told the US-based campaign group that troops from Uganda allegedly carried out the killings on 31 July.
Neither the AU nor the Ugandan government has commented yet on the details of latest allegations.
BBC Africa Live: News updates
Witnesses say that following a bomb attack on an AU convoy in Merca, which is  some 70km (45 miles) south of the capital, Mogadishu, Ugandan forces entered several nearby houses.
"At one house, where the Moalim Iidey family was celebrating a wedding, the soldiers separated the men from the women and shot the six adult men - four brothers, their father, and an uncle," HRW said in a statement.
"Four died immediately, one brother hid under a bed after being shot but later died, and the father died during the night after the soldiers allegedly refused to allow the family to take him to the hospital," it said.
One witness told HRW that before the alleged killings, most people in the area had fled, fearing reprisals after AU convoy attack.
Those who had stayed behind expected that they would be protected because they were celebrating a wedding, the witness added.
HRW says witnesses also allege that 11 civilians were killed by AU troops on 21 July in Merca.
None of the survivors of the two alleged incidents interviewed by Human Rights Watch have yet been interviewed by AU investigators, the rights group said.
There has been a renewed offensive by the AU and Somali military in recent weeks in Lower Shabelle region, where Merca is located, aimed at reclaiming territory from Islamists militants.
AU troops have been in the Somalia since 2007 helping various UN-backed governments fight the al-Shabab group - and there is now a force of more than 21,000 in the country. Most of its troops come from Uganda and Burundi.
Somalia has seen clan-based warlords, rival politicians and Islamist militants battle for control since the fall of long-serving ruler Siad Barre in 1991.
Parents have vowed to fight a £50 increase in the cost of bus passes for Kent secondary school students.
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African Union (AU ) soldiers allegedly killed six people at a wedding in Somalia's port town of Merca, Human Rights Watch (HRW) has said.