The trustees of Wheaton College in Norton, Mass., have voted to admit the first male students to the 183-year-old school in the fall of 1988, according to published reports. The trustees' vote was announced by board Chairman Paul E. Gray in a letter sent to alumnae, faculty and students. A copy of the letter was obtained by the Boston Globe. The letter was obtained by the Boston Globe. The letter followed a meeting held in secret by the trustees of the 1,160-student private school to avoid demonstrations by an anti-coeducational group.