Renaissance Accelerated Reader is currently used in thousands of UK schools. It was designed to motivate reading for pleasure while giving teachers the tools to track reading habits, comprehension and progress. Pupils read books of their individual choice and then take a quiz ensuring they understand what they have read. In the UK over 31,000 quizzes are currently available and more than 150 are developed and added each month. An extremely broad range of books have been quizzed, both fiction and non-fiction, including popular books such as the Harry Potter and Diary of a Wimpy Kid, alongside classics such as Pride and Prejudice and Gulliver’s Travels. In addition to these reading practice quizzes, vocabulary practice quizzes test a child’s understanding of particular words, and literacy skills quizzes analyse 24 different areas of higher order thinking skills.

Accelerated Reader gives immediate feedback on each quiz to children and to teachers, and tracks scores, difficulty level and overall comprehension over time. This formative feedback gives pupils confidence, and helps teachers shape reading instruction and offer personalised guidance.

The ATOS Formula

Book difficulty level is determined by the ATOS formula. This is marked on the book, so pupils can make sure that they are choosing books that are not too easy or too hard – challenging without causing frustration. ATOS uses four factors to determine readability: average sentence length, average word length, word difficulty level and the total number of words in the book. The entire book is scanned and the formula applied to the whole book – not a small sample of text as with other formulae. ATOS can be applied to all publications. In order to relate the ATOS levels to the British system, ‘1’ would have to be added to bring the difficulty level up to English, Welsh and Northern Irish Years and ‘2’ added to bring it up to Scottish P years. The interpretation takes this into account.

As demonstration, ATOS was applied to about 30 text samples from some common UK publications. Interestingly these common periodicals were not as different in terms of their average readability as might have been expected, but the range of readability of items within each one was considerable. An exception was Hello magazine, which had many text samples within a narrow range of readability, as if its policy was to constrain readability deliberately. The Economist had consistently high readability text. The differences in size of text sample were also interesting – the Sun had some shorter but also some longer pieces while Hello texts were even more varied.

The complexity of any text can be determined by the online ATOS Analyser at

Publication Reading Age Range Based on Word Count
The Economist 13.6 12.0 – 15.2 500 – 2,000 words
The Times 12.7 11.0 – 15.1 500 – 800 words
The Daily Mail 12.0 9.1 – 14.2 450 – 700 words
The Sun 11.5 9.7 – 13.3 350 – 1,000 words
Hello Magazine 11.4 9.5 – 13.3 250 – 2,000 words