Armani Taasse was left by the side of the road - having to be rescued by her nan after she rang her for a lift.
See also: Is your old fiver worth a fortune?
The 11-year-old had been given £1.50 by her mum to catch her usual school bus at 8am yesterday.
But the driver refused to accept the £1 - forcing her to find another way to get to Moorside High School, three miles away.
Transport operator D&G has now apologised for the 'misunderstanding' after mum Janice Taasse complained.
Armani, from Bucknall, Stoke-on-Trent said she's been left 'upset and 'embarrassed' following by the incident.
She told The Stoke Sentinel: "The girl in front of me had an old £1 coin and the driver asked her to swap it which she did.
"I knew then that there might be a problem when I went to pay so I told him straightaway that I had the old £1 coin and he said 'I'm sorry but we can't take it' and that I couldn't go on the journey.
"He drove off with me at the bus stop."
Janice, 52, was at work at the time as a care support worker.
She said: "I was at a client's house on Monday morning when I received a call from Armani saying she had been kicked off the bus because she had the old £1 coin.
"I was stuck because I was caring for a vulnerable lady but my vulnerable daughter was left at the bottom of Werrington Road on her own.
"Her nan had to take her to school eventually.
"I rang D&G because I was absolutely horrified. The person on the phone apologised and said it was because the company was banking this week.
"I think the bus driver should have taken her regardless.
"It wouldn't surprise me if other children have been affected. She was upset and it made her feel stupid. She was very embarrassed that it happened in front of everyone."
From October 15, shops can refuse the old version of the coin - but most banks and Post Office counters will continue to accept them from customers.
About 1.2 billion of the old coins have so far been returned - but an estimated 500 million are still in circulation.
A D&G Bus spokesman said: "We are aware of an issue with one of our drivers on Monday morning. This was caused by a misunderstanding of information which we provided regarding the old £1 coin.
"We have since spoken to the driver to ensure this will not happen again and we apologise for any inconvenience caused."