Children with special needs were told by a train manager to sit on the floor of the carriage so they didn't 'spoil' the journey of passengers in the first class coach.
The children – from the Stage Right Theatre Group – were travelling back to Motherwell from a visit to the Edinburgh Fringe festival when they boarded the packed CrossCountry train.
Their carers were forced to make the children - some as young as four - sit on the floor outside the toilets, and, upon seeing a near-empty carriage, asked the train manager if they could instead be seated there.
They were then stunned to be told that the first-class passengers 'do not need the likes of your children spoiling their journey'.
The Metro reports that even though other families with standard tickets were being allowed into first class, the female manager would not be swayed.
She is further reported to have threatened to throw the entire group of the train if they didn't stop 'talking' to her.
Rebekah Aitken, 25, who runs the Stage Right Theatre Group was left furious by the woman's treatment. She told the Daily Record it was discrimination.
"We were discriminated against because of the disabled kids we had with us," she said.
"I'm embarrassed for the kids as they were paraded in front of the passengers and made to feel like an inconvenience.
"The train manager thought they weren't of the standard to be allowed to sit in the business carriage but she moved other kids and parents, who had paid the same train fare, into those seats."
Her business partner Elaine Berry added that the children's memories of the trip to the Fringe are now only of the train journey home.
A spokesperson for CrossCountry trains apologised and said they would be investigating the 'disappointing' allegations.
"We are sorry to learn of the circumstances of the Stage Right Theatre School on their recent journey," he said. "We expect our staff to be polite and helpful at all times and it is extremely disappointing if their behaviour was as described. We will investigate the circumstances as a matter of urgency and will be in touch with them as soon as this is completed."
He added that the company offered their 'sincere apologies to Rebekah, Elaine and all the children for the poor quality of their journey back to Motherwell'.