"As a mother, just getting used to leaving my own child at the school gates, it is clear to me that it takes a whole community to help raise a child", she said, as quoted in People.
George was instead accompanied by his father, Prince William, the Duke of Cambridge, on September 7, when he started his school year at the private Thomas's Battersea School, located in an upper middle-class London neighborhood just a few miles from Kensington Palace.
The night before, the Duchess attended a gala for the mental health charity, the Anna Freud National Centre for Children and Families.
In her speech, Middleton explained that supporting the mental health of students, plus teachers and parents, was a top priority.
"When I came to this conference two years ago, I left with a real sense of energy and passion about what we could all achieve together", she continued.
In October, she debuted her growing baby bump in honor of World Mental Health Day.
Catherine, Duchess of Cambridge, attends The Royal Variety Performance at the London Palladium, Nov. 13, 2014 in London.
He outing comes just days after it was revealed Kate is thinking about home-schooling Prince George after a frightening terror threat was made against the royal last week.
She added, "We are all working to give children the emotional strength they need to face their futures and thrive".
The Duchess of Cambridge is now pregnant with her third child with Prince William, but made a solo appearance at today's event. She appeared fresh and ready for the day ahead, following her appearance at a gala dinner the previous evening, where she wowed in the Zarita lace gown, by Diane Von Furstenberg.
Kate, who is patron of Place2Be, took a break from royal duties at the very start of her pregnancy as she suffered from severe morning sickness.