A shop appeared to ban children from a state comprehensive but not those from a £31,000-a-year private school.
The sign at the entrance of the Co-op branch warned only two Ralph Allen students at a time would be allowed into the store.
But it made no reference to limit the numbers of children from the grand Prior Park College, an independent Catholic school set in a mansion, just under half a mile away in Bath, Somerset.
The manager of the store insisted the sign had been made for the right reasons.
It is said the sign has since been amended to read pupils, rather than Ralph Allen pupils specifically.
Ralph Allen School, less than a mile away from the Co-op, is one of a few schools in the area.
With its sixth form, it serves more than 1,000 pupils and was rated Good by Ofsted in its last inspection.
When asked about the sign, a spokeswoman for Ralph Allen the school had no comment to make.
Metro.co.uk has contacted Co-op for comment.