HVS began with a request in 1973 from Camphill Copake, whose kindergarten for coworker children was outgrowing its space. In September 1973, the school opened with kindergarten and four grades. The Camphill children were joined by children from the wider Columbia County community, primarily from the Taconic Hills School District. Over the next few years, the school grew rapidly. At the time, there were two buildings: a kindergarten and a lower school building. Hawthorne Valley had about 150 students in 1978, the year the first eighth graders graduated and headed off to attend local public and private high schools.
In the fall of 1979, after the graduation and dispersal of the second eighth grade class, the HVS faculty met with one of the school’s senior advisors, Francis Edmunds, who recommended opening a high school without delay and bringing back as many of the graduated eighth graders as possible. The school immediately began recruiting high school students and teachers, and planning a high school building. “The Slice,” as it was termed, built with help from teachers, students, and parents, opened in the fall of 1980 and housed six ninth graders, six tenth graders, and a small faculty that included three full-time teachers (Nick Morrow, Robert Oelhaf, and May Eliot). By 1983, when the first class of seniors graduated, the high school had grown to about 40 students.
In the spring of 1988, a fire destroyed much of the lower school building. Many students finished that school year in donated spaces in Harlemville, and work began posthaste to expand “The Slice” into the main Hawthorne Valley Waldorf School building, with a high school wing and a wing that housed the third through eighth grades.