Implementation of the High Schools That Work (HSTW) key practices improved achievement for career-bound students in these four ways: (1) HSTW sites showed significant improvement in average reading and math scores; (2) the percentage of career- bound students meeting HSTW performance goals in 1994 and 1996 increased from 33% to 43% in reading and from 34% to 44% in mathematics; (3) the gap widened between HSTW career-bound students and vocational students nationally; and (4) a large proportion of the 260 sites assessed in 1993/94 showed improvement in 1996. Mathematics achievement for African-American HSTW youth did not improve between 1994 and 1996, and over half of the career-bound students fell short of the HSTW performance goals in math, reading, and science. Successful HSTW sites do the following: set high expectations; offer intellectually challenging occupational studies; increase access to academic studies that teach essential content from college preparatory curriculum; require a challenging program of study consisting of an upgraded academic core and a major; provide a structured system of work-based and school-based learning; enable academic and vocational teachers to plan together; engage each student actively; involve each student and his or her parents in planning a high school program of study; provide extra help; and use student assessment to advance student learning. (Includes 3 figures.) (MO)