A 1997 longitudinal study of 19 prevention programs undertaken by the U.S. Department of Education noted these key findings:

• Some drug prevention programs improved student outcomes but effects were small. Student outcomes were somewhat better in districts where the prevention programs had greater stability over time and in districts with more extensive program components, including student support services.
• Few schools employed program approaches that have been found effective in previous research. The consensus of the current research literature is that certain approaches, such as those that teach children how to resist and deal with powerful social influences for using drugs and those that correct those misperceptions of peer drug use, have the greatest potential for making a difference for students. However, these approaches are rarely implemented. A likely reason is the higher cost of these program approaches, particularly in terms of teacher training and staff time.
• Program delivery was variable and inconsistent, even within schools. To increase the likelihood that a program will be delivered faithfully, teachers must be given proper and sufficient training so they will be confident and prepared to deliver the program. Many of the approaches that aim to teach students how to resist and deal with social influences, for example, require teaching methods that are very different from the traditional methods that most teachers employ in their classrooms. These approaches utilize role-playing, small-group discussion, and other interactive methods and often use peer leaders to deliver portions of the program. Teachers may be more reluctant to use these types of approaches because they require more intensive training, more time in the classroom, and more planning.
• Few districts seem to know about or consider research findings when planning their prevention programs. Only a few districts engaged in a well-defined process of developing their programs. Such a process would include the following:
• Assessing the problems of students in the district's schools and in the community
• Setting priorities for how to address these problems.
• Reviewing relevant research that links these problems and priorities to effective strategies
• Selecting strategies that appear to have promise for their district.
• Providing the leadership and training necessary to implement the selected strategies
• Assessing progress in meeting the needs identified in the first step
• Adjusting program strategies accordingly
• Few districts also conducted formal program evaluations to assess their program's effectiveness and identify areas in need of improvement.

While all school districts conducted informal assessments of their programs periodically, fewer than half conducted and responded to the evidence of more formal evaluations in selecting or altering programs.

Source: Silvia, E.S., & Thorne, J. (1997). School-based prevention programs: A longitudinal study in selected school districts. Executive Summary. Final Report. Washington, DC: U.S. Department of Education.