Final answer:
A third-grade teacher should use a screening measure that evaluates the ability to represent phonemes with letters for assessing risk of reading failure, as it is a critical skill in reading development.
Step-by-step explanation:
A third-grade teacher wanting to assess whether any students are at risk for reading failure should use a screening measure that evaluates their ability to represent phonemes with letters (as shown in spelling samples). This skill, which involves associating sounds with their written form, is essential for reading development. Screening measures might assess the ability to segment phonemes and manipulate phonemes, which are also important foundational skills for reading. However, the ability to connect phonemes to their corresponding letters indicates a student's grasp of phonics, which is crucial for decoding words and is a strong predictor of future reading success. It is important for educators to recognize the signs of dyslexia, a common reading difficulty, where students may experience challenges in processing letters and sounds accurately.