This excerpt is from the U.S. Supreme Court decision in Brown v. Board of Education of Topeka, Kansas (1954). Today, education is perhaps the most important function of state and local governments. ... It is required in the performance of our most basic public responsibilities, even service in the armed forces. It is the very foundation of good citizenship. Today it is a principal instrument in awakening the child to cultural values, in preparing him for later professional training, and in helping him to adjust normally to his environment. In these days, it is doubtful that any child may reasonably be expected to succeed in life if he is denied the opportunity of an education. In the excerpt from the Court's ruling, what does the word instrument mean