Tonight marked the end of an era as the Carbon County School Directors' Association staged its 67th and last regularly constituted convention in the form of a dinner meeting at Smith's Stoney Creek Hotel in Penn Forest Township. The association will be replaced by the Intermediate Unit, which is composed of 14 directors from Carbon and Lehigh Counties, effective July 1, 1971. The Intermediate Unit, which organized recently, will meet tomorrow night at Slatington High School.