A girl has lost a High Court battle to prevent her school from "requiring or encouraging" pupils to wear a face mask.
She argued they posed "serious harm" to children's physical and mental health.
A request for an interim judgement against the Tapton Academy School Trust, which runs a number of schools in the Sheffield area, was rejected.
As she is not required to wear a mask by her school, the order would be unnecessary, the judge said.
Judge Roger ter Haar QC said: "The case as presently put forward by the claimant suffers from a fundamental defect: the school does not require the claimant to wear a mask - she has been treated as being exempt from that requirement."
He said he drew "no conclusions whatsoever as to the safety or otherwise of requiring children to wear face masks at school".
The Trust had previously said its policy was to "encourage, not to enforce" mask-wearing in order to protect children, staff and visitors.
About 120 employees - more than 10% of the trust's staff - had contracted coronavirus since the end of August 2020.
The girl's lawyers provided a report from a health and safety practitioner about issues children may encounter when wearing face masks, and another expert's report about the psychological risks of a mask-wearing policy.
"Put shortly, the underlying premise of the claim is that the physical and psychological risks presented to children by the requirement to wear face masks is not justified by medical or epidemiological evidence," the judge said.
He accepted it was a belief which was strongly held by many people, including the girl's father.
However, the witnesses' views "do not represent universal scientific and medical views as to the scientific and medical merits, disadvantages and dangers of the wearing of masks in schools," the judge said.