Since moving to post-16 education, the girl, who has not been identified, has not received any financial help to get to the college named in her Education, Health and Care Plan.
The council had argued it does not have a duty to provide transport assistance for the girl because she is in post-16 education and could use public transport, if accompanied.
But an investigation by the Local Government and Social Care Ombudsman, which considers complaints against councils, found the council failed to take into account the actual journey the girl would have to make to get to the college.
The Ombudsman says it did not consider the distance and location of the college meant it would take her significantly longer than the benchmark journey time of 75 minutes – recommended in the statutory guidance – to get there by public transport.
The mother had told the council her daughter’s disability makes it difficult for her to use public transport, that because there is no direct bus link a single journey would take two hours, and that somebody accompanying her "would have to spend all day travelling to and from the school".
Michael King, Local Government and Social Care Ombudsman, said: “This is not the first case in which we have found problems with the way Staffordshire County Council has made decisions about providing school transport.
"Some of the faults we have found in those cases are similar to those here, including not taking individual circumstances into account, and not making decisions in line with its own policy when read in conjunction with statutory guidance.
“I am pleased the council has agreed to my recommendations and hope the learning it will share from this case will help ensure other teenagers are not affected by poor decision making in future.”
The LGSCO said in this case the council has agreed to apologise to the girl and her mother and pay the mother £300 to acknowledge the uncertainty and upset caused by the flawed decision making.
It will also reconsider their school transport appeal, and backdate eligibility to the start of the Autumn 2020 term.
Jonathan Price, Staffordshire County Council’s Cabinet member for Education and SEND, said: “We have apologised to the family and put right our mistake in this case and are reviewing how we have assessed post-16 transport applications for students with Special Educational Needs and Disabilities.”