We present four studies indicating that the size and design of the typeface in textual material for children aged 7-9 may impair speed of reading and comprehension, and measurement of reading attainment. The first study compared the speed with which sample sentences were comprehended. The sentences were printed in Arial font with an x-height of 4.2 or 5.0 mm. The sentences were verified 9% more quickly when presented in the larger typeface. The second study compared reading age on the Salford Sentence Reading Test when the typeface remained at the initial size (x-height 3.3 mm) throughout the test, and when it decreased in size as usual. The average reading age measured with the larger font was 4 months older. The final studies compared the font Sassoon Primary with the font Verdana and showed that Verdana was read and searched more quickly.