Appendix A.

Summary of language measures obtained at kindergarten, and used to construct the latent measure of language and literacy.

Language Measure	Description
Comprehension	The auditory comprehension subtest of the Preschool Language Scales-4 [1] was used to measure children’s understanding of spoken language, usually involving specific syntactic or grammatical forms. The task requires children to demonstrate their understanding by performing specific commands given by an examiner. Raw scores were used in analysis.
Vocabulary	The Expressive One-Word Picture Vocabulary Test [4] was used to assess expressive vocabulary. For this task, children are asked to provide the words that label a series of pictured items shown one at a time on separate pages. Raw scores were used in analysis.
Narrative skills	A 20-minute narrative sample based on five related themes was elicited from each child. Each narrative sample was scored by three independent viewers. All narrative segments were used to score narrative abilities based on 12 different assessment points similar to many other rubrics [31]. For each assessment, the observer gave a score between 0 and 3, so the final narrative score could vary between 0 and 36. The average score from all three observers was used in analysis. The rubric is presented in Appendix B.
Word reading	Word reading was assessed using the word reading subtest of the Wide Range Achievement Test – 4 (WRAT) [22]. Children are asked to read 55 words aloud. As they progress through the list, the words get harder. If a child makes 10 consecutive mistakes by either pronouncing a word incorrectly or skipping a word the task is stopped. The total raw number of words read correctly was used in analysis.
Reading Comprehension	The Qualitative Reading Inventory (QRI) – 4 [23] was used to assess reading comprehension. Each child read three passages – one narrative written one level below kindergarten (pre-primer), one narrative written at the kindergarten level (primer), and one expository written at the kindergarten level. The child would read each story, retell the story to the examiner, and then answer questions about the story. The raw sum of correct answers (out of 30) to the comprehension questions across all three stories was used in analysis.
Syllable Counting	Syllable counting assesses sensitivity to syllable structure within words. Children saw and heard a man on a computer monitor say a word and were asked to count the number of syllables in the word by tapping them on the table. The percentage of correct answers (out of 48) was used in analysis [17].
Initial Consonant Task	For the Initial Consonant Same –Different task, children saw and heard a male speaker produce two words. The child’s task was to judge whether both words started with the same sound. The percentage of correct answers (out of 48) was used in analysis [17, 24].
Final Consonant Task	In the Final Consonant Choice task, children saw and heard a male speaker produce a target word which the child was to repeat correctly. Three more words were then presented in a similar fashion. The child’s task was to select the word out of the three that had the same ending sound as the target word. The percentage of correct answers (out of 48) was used in analysis [24].
Processing Speed	The object naming subtest of the Comprehensive Test of Phonological Processing [26] was used to examine processing speed. The test consists of two pages, each with four rows of nine pictures of simple objects. Children had to name the objects in order as quickly as possible. Both trials were timed and the time in minutes across both trials was used in analysis.