Until 1977, Cass was Detroit's only magnet school and the only non-neighborhood enrollment school in Detroit. Today, Cass is one of few magnet schools in Detroit. Entrance to Cass is based on test scores and middle school grades. Students are required to choose a curriculum path—roughly equivalent to a college "major"—in the ninth grade. Areas of study include, but are not limited to, architecture, music, business, human services, and chemical/biological sciences.
The school was founded on the third floor of the old Cass Union School in 1907. Its historic landmark building on Second Avenue in downtown Detroit was built in 1917. To the south of it an addition designed by Albert Kahn was built in 1985. The new, modern facilities of the school were built in 2004 in an adjacent lot to the north of the original building on Grand River Avenue.
In 2007 there was a large fire in the old structure. Complete demolition of the vacant Cass Tech building began in June 2011 and was finished by November. Pictures of the old historic structures, both from the outside and the abandoned inside floors and classes, can be seen here . In addition, a 3D floor-by-floor interactive map of the old building is available here  as well.
Following the fire in the old structure, it was demolished and removed by Homrich Demolition. Images and information on the demolition of the structure can be found in the Homrich Demolition project file. At time of demolition, the school building was approximately 830,000 square feet (77,000 m2) and weighed more than 100,000 short tons (91,000 t). Over 90% of the material in the building was recycled for other uses or as backfill.
In 2008 some classes that were not very popular with students were removed due to reduction in teacher staffing due to declining enrollment.
Based on current enrollment information, there are approximately 2,086 students that attend Cass Technical High School. There are 624 students in the ninth grade, 537 students in the tenth grade, 466 in the eleventh grade, and 459 in the twelfth grade.
Of the 2,196 students that attend Cass Technical High School, 1,951 (89.3%) of them are Black or African American, 89 (4.0%) are Asian American, 70 (3.2%) are Hispanic or Latino, 56 (2.6%) are White, 17 (0.8%) are Arab, and 2 (0.1%) are American Indian or Alaska Native.
Cass Technical High School's average ACT score is 21, which is four points higher than the average for Detroit public high schools. Cass offers eleven advanced placement courses including language composition, history, chemistry, calculus, and physics. Students are required to maintain a 2.5 grade point average on a scale of 4.0 in order to retain enrollment. Cass Tech students' strong academic performances draw recruiters from across the country, including Ivy League representatives eager to attract the top minority applicants.
The harp ensemble is usually composed of five well-seasoned student harpists. They each receive private lessons, learning performance skills and the traditional techniques of the Carlos Salzedo Method. The group does perform outside of school related functions.
There are beginner, intermediate, advanced and jazz band classes, as well as a marching band. The CTMB (marching band) has performed for Patti Labelle, Sinbad, and Jay-Z as well as at various college and university, and homecomings. The marching band was also a part of the 2007 FedEx Orange Bowl in Miami, Florida, but was not televised. In 2008, the band performed at Texas Southern University. In 2010, the CTMB participated in Norfolk State University's Homecoming and won first place in the McDonald's Battle of the Bands. In 2013 CTMB went to the 2013 inauguration for President Barack Obama.
The 2005–2006 Cass Tech String Quartet was the winner at the 2006 MASTA state-wide chamber music competition. The quartet was also featured in the 2006 Michigan Youth Arts Festival. The Cass Tech Chamber String Orchestra, the school's advanced orchestra, participated in the All City High School Symphony Orchestra program at the Renaissance Center's Ambassador Ballroom on March 8, 2007.
Cass Tech's track and field history goes back to 1926 when Eddie Tolan and his teammate Loving won the interscholastic track meet at Northwestern University. Tolan came to be known as the "Midnight Express". He set world records in the 100-yard dash and 100 meters event and Olympic records in the 100 meters and 200 meters events. He was the first African-American to receive the title of the "world's fastest human" after winning gold medals in the 100 and 200 meters events at the 1932 Summer Olympics in Los Angeles. In March 1935, Tolan won the 75, 100 and 220-yard events at the World Professional Sprint Championships in Melbourne, Australia to become the first man to win both the amateur and professional world sprint championships. In his full career as a sprinter, Tolan won 300 races and lost only 7.
Program is the largest organization in the school. It has a curriculum that includes Leadership Lab and Cadet Challenge, a drill team, and an honor guard team. The drill team is composed of: a First-Year Color Guard, an Open-Year Color Guard, an Armed Exhibition Team, an Unarmed Exhibition Team, a Female Armed Exhibition Team, an Unarmed Regulation team, and an Armed Regulation Team. The Armed Exhibition Drill Team was founded by Cadet Colonel Anthony James Cole (City of Detroit Corps Commander 1997–1998) in 1996, which opened the door for the Unarmed Exhibition Team and the Female Exhibition Team. The JROTC program has the "Gold Star Insignia", which is the highest attainable rank in the JROTC program, and has been maintained by the school since the early 1990s. In 2005, the Cass Tech Renegades Drill Team was selected to attend the National Drill Competition held in Daytona Beach, Florida. It was the first invite for the state of Michigan. The following year, the team was invited to return, leaving ranked fourth in overall performance. The honor guard team has attended many events throughout the city, including many parades and grand openings, as have the color guard and exhibition teams.
Diana Ross, singer, actress-Graduated 1962, one full semester ahead of her classmates. Ross' major as listed in the Cass Tech Triangle Yearbook was "Home economics." Ross studied costume design as her curriculum path.
Esther Gordy Edwards, former staff member and associate of her younger brother Berry Gordy's fabled Motown label during the 1960s. Edwards created the Motown Museum, Hitsville U.S.A., by preserving the label's Detroit studio.