Cherie Booth QC, Tony Blair's wife, argued that the dress ban prevented Shabina Bingham, now 17, from following her religious beliefs.
But the Law Lords disagreed, overturning a Court of Appeal Judgement. Denbigh High School in Luton were right to enforce the rule, they said, but it should not be interpreted as an all out ban in every school across the UK.
European courts upheld one ban in December 2005, arguing that no one religion should be given preference.
"I don't understand why they told me to go home just because I wore six more inches,'' Begum said after the decision.
The school is 79 percent Muslim and allows students to wear a headscarf, or hijab.
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Bloomberg, Wed 22 Mar 2006 at 4:39pm