This digest in Spanish describes several technologies that can be used to control access to, and improve surveillance of, school grounds. Access can be controlled by using "smart" cards to control keyed entries. Many schools have problems with multiple copies of keys, and these card systems are integrated with computer software that allows for specific coding and specific access. Such cards can also be immediately canceled in the event of loss or theft and can be used to control entrances to parking lots and other school property. Another security device, metal detectors, can be helpful in ensuring the safety of a school but should be employed only in those schools where the risk is the highest. These detectors are expensive and require additional employees to operate the equipment. Another option is an alarm system that can be used to detect smoke or fire, intruders, and other threats to safety. Surveillance equipment is another possibility, and it too can vary widely in cost and in sophistication. However, even with digital technology, surveillance remains more useful as a means of reviewing incidents rather than in stopping behavior as it occurs. Before investing in any system, schools should identify the specific problems that need to be solved. (RJM)