Graduated class are individuals who have gone to the school being referred to yet are no longer there. Perhaps they graduated, or possibly they didn't complete the course.
It's from Latin: a former student is a male individual who has gone to the school being referred to, and an alumna is a female individual who has gone to it. (The Merriam-Webster webpage says a former student could be either a man or a lady.) However, in any event in the US, individuals some of the time utilize "graduated class" as a solitary term: "I am a graduated class of the building school." Not that many individuals here learn Dissertation Help Latin any more.
So the graduated class of a designing school are the general population who used to go to that school.