A scale for measuring ability in spelling prepared by Dr. Leonard P. Ayres arranges the thousand words most commonly used in the order of their difficulty. From this sheet it is possible to discover words of approximately the same difficulty for each grade. A test could therefore be derived from this scale for each of the grades with the expectation that they would all do about equally well. There would also be the possibility of determining how well the spelling was done in the particular school system in which these words were given as compared with the ability of children as measured by an aggregate of more than a million spellings by seventy thousand children in eighty-four cities throughout the United States. Such a list could be taken from the scale for the second grade, which includes words which have proved to be of a difficulty represented by a seventy-three percent correct spelling for the class. Such a list might be composed of the following words: north, white, spent, block, river, winter, Sunday, letter, thank, and best. A similar list could be taken from the scale for a third, fourth, fifth, sixth, seventh, or eighth grade. For example, the words which have approximately the same difficulty,--seventy-three percent to be spelled correctly by the class for the sixth grade,--read as follows: often, stopped, motion, theater, improvement, century, total, mansion, arrive, supply. The great value of such a measuring scale, including as it does the thousand words most commonly used, is to be found not only in the opportunity for comparing the achievements of children in one class or school with another, but also in the focusing of the attention of teachers and pupils upon the words most commonly used.[25]