Daniel H. Coughlin, 65, a retired high school teacher who wrote about his experiences in the Vietnam War, died Thursday in his home. Born and raised in Flatbush, Brooklyn, he served in the U.S. Army’s Third Brigade, 82nd Airborne, in Vietnam from June 1968 to July 1969. Dedicated to his students, Coughlin taught Social Studies at Canarsie High School and was awarded two certificates by the City Department of Education for his work in the school’s in-house program for troubled students. He was also recognized for his accomplishments as a teacher in the publication “Who’s Who Among America’s Teachers.” Fond of golfing and fishing, he was also an avid Mets baseball fan and a season ticket holder for the New York Giants football team. He retired in 2010 after 20 years. Surviving, along with his grandsons and his wife, are his son, Richard Alexander, and his daughter, Christine Alexander. Coughlin’s funeral was held on Monday at the Colonial Funeral Home in New Dorp and burial followed in Greenwood Cemetery, Brooklyn.