The PRETOS are broad measures of a child's ability to discriminate between misspelt words and correctly spelt words, presented in the context of meaningful paragraphs. The tests provide a measure of spelling achievement within the context of a proofreading task, as well as giving diagnostic information about individual pupils' spelling accomplishments. The abilities tapped by the PRETOS are broader than those associated with the traditional assessment of spelling.

Each test is made up of three or four paragraphs containing 12 – 14 lines of text, with two lines having no misspelt words.

Norms are provided from March to November, and class percentile ranks are provided for both production and recognition scores. The production score is a measure of the child’s ability to spell a word correctly after identifying it as an error, and to locate the error-free lines. The recognition score is a measure of the ability to recognise misspelt words.

The format of the tests also provides specific information on misspelt words that are identified and re-spelt correctly, misspelt words that are identified but not re-spelt correctly, misspelt words that are not identified, correctly spelt words that are identified as misspelt, and words that are incorrect because of context, rather than because of “spelling”.