In fall 1985, the San Jose/Evergreen Community College District began using a computerized prerequisite checking system to strengthen academic standards. Over the next 4 years, the computerized system shifted from an informational mode, which merely indicated whether a student met course prerequisites or not, to a lock out mode, which prevented a student who had not met course prerequisites from registering for that course. In 1989, a study was conducted to assess the impact of the lock out mode on enrollments. Computer records were analyzed to determine the number of students not meeting prerequisites in each discipline, reasons for students being listed as not meeting a prerequisite, and the characteristics of the disciplines most affected by being placed on lock out mode. Study findings included the following: (1) as course prerequisites were more strictly enforced and as the data in the computer became more accurate and complete, the total percentage of students who attempted to enroll in courses without meeting prerequisites dropped from 41% in fall 1985 to 6% in fall 1988 and 2% in spring 1989; (2) in spring 1989, 2% of the students in the district insisted upon taking courses for which they did not meet prerequisites; (3) students listed as not meeting a prerequisite generally did not have the basic skills prerequisite for the class, did not have the course prerequisite, or had taken the prerequisite course at another institution; and (4) in general, the disciplines most affected by the lock out mode had complex prerequisites, had basic skills as well as course prerequisites, had low levels of basic skills, or enrolled large numbers of well-educated students. Tables and graphs (the bulk of the document) showing the decreasing numbers of ineligible students by year and discipline are attached. (JMC)