THE STUDY CONCERNED TRACING THE DEVELOPMENT OF LANGUAGE PROFICIENCY IN THE SAME GROUP OF SUBJECTS FROM KINDERGARTEN THROUGH GRADE 9. THE RESEARCH WAS BASED ON A STUDY OF THE PATTERNS AND BEHAVIOR OF THE SUBJECTS' SPEECH AND WRITING AND THEIR COMPETENCE IN READING AND LISTENING. SUCH INFORMATION IS USEFUL IN CURRICULUM PLANNING AND IN DEVELOPING TEACHING METHODS. THIS STUDY CAN ALSO CONTRIBUTE TO A BETTER UNDERSTANDING OF THE DIFFICULITIES AND SUCCESSES HUMAN BEINGS ENCOUNTER IN DEVELOPING POWER OVER LANGUAGE IN ITS MAJOR ASPECTS--SPEAKING, WRITING, READING, AND LISTENING. THE FOLLOWING HYPOTHESES ARE AMONG THOSE WHICH WERE TESTED--SUBJECTS WHO HAVE DEVELOPED SKILL IN THE SPOKEN LANGUAGE ALSO DEVELOP THE SKILLS OF WRITING, READING, AND LISTENING MORE FULLY THAN THOSE WITHOUT SPOKEN LANGUAGE SKILL, SUBJECTS WITH HIGHEST SCHOOL ATTENDANCE RECORDS WILL RANK HIGH ON DEVELOPMENT OF SKILL IN LANGUAGE, SUBJECTS WHO HAVE THE MOST INTERACTION WITH OTHER PERSONS WILL DEVELOP LANGUAGE SKILLS MORE RAPIDLY THAN THOSE OF LIMITED CONTACT, SUBJECTS FROM HIGH SOCIOECONOMIC STATUS WILL DEVELOP LANGUAGE MORE RAPIDLY AND COMPETENTLY THAN THOSE OF LOWER STATUS. SEVERAL SIGNFICANT FEATURES EMERGED FROM THE WORK DESCRIBED IN THIS REPORT. IT APPEARS THAT THE GREATEST MEASURE OF LANGUAGE PROFICIENCY IS NOT BASIC SENTENCE PATTERN, BUT WHAT IS DONE TO ACHIEVE FLEXIBILITY WITHIN PATTERN. COMPETENCE IN SPOKEN LANGUAGE HAS PROVED TO BE A NECESSARY BASE FOR COMPETENCY IN WRITING AND READING. FINALLY, THE PERSISTENTLY PARALLEL VARIATION OF LANGUAGE PROFICIENCY AND SOCIOECONOMIC STATUS SHOULD NOT BE OVERLOOKED.