The Princess of Wales introduced a new phase in her early years campaign at the National Portrait Gallery in London

Kate, the Princess of Wales, went back to school Tuesday, joining a group of young students on a field trip. The 43-year-old princess, a mother of three herself, surprised visitors outside the National Portrait Gallery in London when she stepped off a bus with a group of 4 and 5-year-old students from All Souls CE Primary School.

Britain's Princess Kate accompanied a group of pupils on a school trip to London's National Portrait Gallery on Tuesday (February 4). US says will levy tariffs on Mexico, Canada and China on Feb. 1

WPA Pool/Getty Images Princes Kate Middleton held hands with young children during a royal visit to London's National Portrait Gallery on Tuesday, February 4. Kate, 43, was "like one of the moms" as she boarded a school bus,