"Former schoolmates" refers to people who used to be classmates or attend the same school but are no longer students at that school. They have now moved on to different schools, graduated, or are no longer enrolled in education. Full definition
In the case of a high school offering the use of free social media to keep alumni up to date with school events and connect with former schoolmates in exchange for authentic user profiles - that is, using real names and authentic records - which will be used to deliver targeted advertisements, 51 percent are opposed to the idea. (techtimes.com)
Those are precisely the words numerous former schoolmates at Stoneman Douglas used to describe Cruz. (miamiherald.com)
And today Cameron does not have to look hard to find former schoolmates in the ranks of the new Tories. (channel4.com)