About 100,000 teenagers joined the military in 2004. Nearly 57 percent of all Army, Navy, Marine, and Air Force recruits are 17 to 19 years old. That means military recruiters, or officers in charge of finding volunteers, are very interested in speaking with high school students. A law passed in 2001 says that recruiters must be allowed to visit high schools twice a year. Schools must also give recruiters students' phone numbers and addresses.