The Oscar-winning star, who lives in Nairn, said an Oxford professor had told her that state education was so under question the top university "longed" for Steiner pupils who still have a love for learning.
Swinton, 52, spoke out at an open day for the Moray Steiner School and the recently opened Drumduan Upper School in Forres, Moray. She is a trustee of both schools and a co-founder of Drumduan, where Xavier and Honor, her 15-year-old twins with artist John Byrne, are pupils. The London-born actress said there was "a misunderstanding" about Steiner education.
She added: "When I went into the Steiner school for the first time, I was struck not only by the trusting and familial atmosphere for younger children, but mainly by older children, because I had never walked into a school before where teenagers had been so welcoming and self-possessed and kind. Older children play with and care for the younger children."
Steiner schools are based on the philosophy of Rudolph Steiner who founded the first in Germany in 1919.