There is considerable variability in the literacy assessments taken in Kindergarten through second grade, across schools and between multilingual learners and other students, and within students over time. This makes it difficult to study changes in students' acquisition of ELA skills in these formative years, or to evaluate policies and practices meant to support literacy development. Here we examine several popular early grade assessments--the MAP, ACCESS, DIBELS, TRC English & Spanish versions, and apply a novel approach to combining information to develop latent scores of students' literacy development. We find each assessment provides information that is predictive of students' development towards third grade literacy outcomes (ELA grades and state assessment scores), with different strengths and weaknesses, and considerable overlap among them. We further provide evidence of strong predictive validity for the combined scale, even in post-COVID-19 years, suggesting that we could leverage existing assessment information to produce metrics for studying school, district, and state policies and practices around literacy development. [The Chicago Public Schools partnered in this study.]