Arthur L. Johnson High School, better known as ALJ or Johnson, is the public high school for students in Clark and Garwood. The school offers a wide variety of courses, twenty Advanced Placement (AP) courses, 26 different clubs and 22 interscholastic varsity sports. The student run morning daily television show (ALJ Today), provides students with information about school happenings and opportunities.

The school was recognized as one of the Top American Public High Schools by Newsweek magazine for 2010. Some notable graduates are Frank Spaziani, the head football coach at Boston College, and Kenneth Ham, a NASA astronaut.

The school building underwent a major renovation completed in 2008, with the science labs and auditorium renovated the following year. The principal of Arthur L. Johnson High School is Rick Delmonaco and the assistant principal is Travis Smith. The supervisor of pupil personnel services is Colleen Gialanella and the supervisor of athletics is Gus Kalikas.