Parents claim bikes were barred from the grounds of 'eco-friendly' Risca Primary in Newport, Gwent, while risk assessments are carried out.
Ceri Jeffries, 32, said her three kids, all aged 10, usually travelled in a group with four other children but would now have to chain their bikes outside the school gates.
She said: "The school is eco-friendly and encourages healthy eating and lifestyles yet it is stopping children from riding bikes, which is doing the opposite. It is ridiculous. I cycled there as a child. A lot of kids and their parents are upset."
She said a teacher told her daughter in an assembly that the bike sheds were being flattened to make way for a new car park.
Ceri added: "As soon as she told me this I called the school and spoke to the deputy head teacher who confirmed this."
She also said she was told safety measures which are brought in for the annual three-week cycling safety course could not be made permanent.
Rachel Guy, mum of two children who have ridden to Risca in defiance of the ruling, branded the policy ridiculous.
Head teacher Jayne Arthur said: "We are working with the council's road safety and health and safety teams to review the situation and complete a risk assessment and traffic survey of the school site.
"Ensuring pupils' safety and wellbeing remains our utmost priority, and we are seeking to resolve this issue as soon as possible."
Risca is part of the Eco- Schools scheme which promotes sustainability.
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