Ashcombe Primary School - which teaches students aged four to 11 - has threatened to confiscate any cards found on the premises in Somerset, southwest England, the Times reported.
"Some children and parents encourage a lot of talk about boyfriends and girlfriends," wrote head teacher Peter Turner in a monthly newsletter.
"We believe that such ideas should wait until children are mature enough emotionally and socially to understand the commitment involved in having or being a boyfriend and girlfriend," he said in the letter to parents.
But the head teacher of the school, which has 419 pupils, came under fire for the Valentine card crackdown.
Rajeev Takyar, whose children Jai, 11, and five-year-old Aryan, are pupils there, blasted the ban as "ridiculous".
"Whatever is going to be next? Banning them stops children from having social skills. How are they going to learn about relationships otherwise?"
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