This study validates and standardizes the EACOL, a tool for teachers to assess the Portuguese-language reading (silent and aloud) of 2nd-to-5th-grade students. 72 teachers were asked to answer the EACOL and the Strengths and Difficulties Questionnaires screening behavioral scale. 452 pupils performed a test battery composed by a general cognitive ability test and seven reading measures: Reading Performance Test, a Word and Pseudoword Reading Task (accuracy and accuracy rate measures), Reading Comprehension Test, and General Reading dimension reduction Composite. The instrument presented high internal consistency and moderate-to-strong correlations with all seven reading variables; cluster analysis suggested the existence of three proficiency groups (poor/average/good readers). This robust results attesting that the teachers, when provided with sound criteria, can come to reliable evaluations of their students’ reading ability. Discussion of discriminant validity is provided. With this final version of EACOL, we hope to offer to Portuguese-speaking researchers a validated instrument to indirectly assess the reading ability of schoolchildren, and to set out a model that can be adapted to other contexts.