Very occasionally, teachers may consider retesting a student with LADS Plus after they have already been tested on it before. Although there may be a valid motive for wanting to do this, generally it is not a good idea because the results of a retest could be misleading for reasons that are explained in Section 3.3.2.
Possible reasons for retesting
Before going any further, however, it is essential for the teacher to stop and reflect on why it might be appropriate to retest a student. Sometimes teachers (or parents) are unwilling to accept the result of the first screening at face value because it does not conform to expectations. When considering this issue it is important to bear in mind that LADS Plus is a fairly quick screening test and, like all screening tests, is not infallible. Its advantages are speed combined with an accuracy level that is generally very good for detecting the most common cases of dyslexia where the underlying problems are in phonological skills and verbal memory (see Section 2.2). But on a very few occasions LADS Plus may get it wrong. In particular, less common types of dyslexia, such as those where the underlying problems are in visual-perceptual or visual-motor skills, are less likely to be detected by LADS Plus. If the student’s problems are in the latter aspects of cognition then retesting with LADS Plus is unlikely to shed any light on the matter and it would probably be better to consider alternative forms of assessment or seeking professional help from an educational psychologist.
Another situation where retesting might be under consideration is where the student was unwell at the time or the first screening, or not appropriately motivated, or distracted, or failed to understand exactly what was required of them. As explained in Section 3.2, the proper course of action is to ensure that the conditions necessary for effective screening are met before embarking on screening in the first place.
Why is retesting not recommended as a general rule?
The chief reason why retesting is not usually a good idea is because all psychological and educational tests are subject to practice effects, which are the positive or negative psychological impacts of previous assessment(s) on a student’s performance. Positive impacts, which include factors such as item familiarity and increased confidence as a result of previous experience with the tasks, tend to inflate scores on subsequent assessment occasions. Negative impacts, which include factors such as decreased motivation due to boredom with the tasks or overconfidence as a result of feedback from previous assessments, tend to deflate scores on subsequent assessment occasions. Furthermore, practice effects will not necessarily affect all students to the same extent. Some students may experience more negative effects while others may experience more positive effects. In general, the magnitude of practice effects is a function of how often students have been assessed on this or similar tests and the time interval between assessments. Both positive and negative psychological impacts tend to decrease as the time interval between assessments increases.
It can be seen, therefore, that retesting with any psychological and educational test is highly likely to produce results that have been influenced in some way – either positively or negatively – by the original assessment, and as a consequence are less likely to be valid or reliable.
Exceptions to the general rule
There are exceptions to the general rule. Some tests (but not LADS Plus) have parallel or equivalent forms that are designed specifically for resting. Here the format and nature of the two forms of the test are the same, but the actual items are different. This eliminates some but not all of the undesirable practice effects of retesting so even in this situation caution should be exercised when interpreting results.
However, exceptional situations may arise when even the most conscientious teacher feels the needs to re-administer one or more of the tests in LADS Plus because it was discovered after the original screening that the student was unwell, or where a fire drill interrupted the assessment, or if the student was clearly not applying proper attention or effort to the tasks. In such cases, the results are unlikely to give a true indication of abilities and it is permissible to re-test the student but only after an appropriate length of time has elapsed. Professional opinions differ somewhat on this matter – some authorities recommend at least a year between tests, while others suggest that six months is acceptable. Certainly, the minimum interval that should be considered is a full term or semester, even when parallel or equivalent forms are being used. The point is that enough time should have passed to reduce the risk not only of remembering items significantly but also of being demotivated by being confronted with the same test yet again. Of course, it is important to ensure that the student is properly prepared for the retest, including explaining why the retest is necessary. The first result should be discarded and the second result should be regarded as being more likely to reflect the ‘true’ abilities of the student.
If it is considered essential to have answers regarding a student’s educational problems sooner rather than later, then instead of rescreening before an acceptable interval has elapsed it would be better to use other types of assessment or to obtain a psychological assessment from a suitably qualified psychologist.