To the Editor: I was astounded by the negative reaction of residents of Lockney, Tex., when Larry Tannahill, the father of a 12-year-old, challenged the school district's drug-testing policy in court (front page, April 17). Last summer my family challenged our board, which requires urine tests for certain academic classes. I want to show my support for Mr. Tannahill, and wish that residents of Lockney who support him behind the scenes would also support him in public. We should remember this quotation from William O. Douglas, the Supreme Court justice: [continues 62 words]