American schools主语
both public and private对主语的限定和补充,同位语
consist of谓语
12 years of grades- basically 8 years of eelementary school and 4 years of secondary of high school 宾语
although连词连接从句
grades 7 and 8, of 7,8 and 9从句主语
may be housed从句谓语(被动)
together in a middle school of junior high school从句状语.