The term ELEM. SCH. SUBJ. is an abbreviation for Elementary School Subject, and the crossword solution ARITH is an abbreviation for Arithmetic. Arithmetic is a branch of mathematics that deals with the study of numbers, their operations, and their properties. It includes topics such as addition, subtraction, multiplication, division, fractions, decimals, percentages, exponents, and roots. Arithmetic is a fundamental subject taught in elementary schools and is essential for students to understand basic math concepts.