At Westgate Elementary in Lakewood, first grade teacher Sarah Bardon knows which of her students are right on track with their reading, and which ones are struggling.
"I have some students reading 120 words a minute and others who are reading five," Bardon said.
Those struggling students are the ones state lawmakers had in mind when they passed the "Reading to Ensure Academic Development" - or "READ" Act.
In 2013, it replaced the Colorado Basic Literacy Act, bringing a new focus to students with serious reading deficiencies.
Alisa Dorman, Executive Director of the state literacy office, says the law asks school districts to screen kids for their reading risk, and intervene on their behalf from kindergarten through third grade.
That's the key year, because after third grade, kids have to be able to read to learn other things.
But what happens when a student reaches that age, and isn't reading well?
Starting in the 2016-2017 school year, the law gives district superintendents the final say on whether or not to hold a child back if they're not making adequate progress.
In the past, that decision has been left to the parent.
The READ Act does not require to hold students back, but they will have more authority on the matter. Still many educators believe holding a child back is never the right answer.
Westgate Elementary School Principal David Weiss says there's plenty of research that shows it can actually do more harm to a student.
Weiss points out that students who are held back may see content they've already seen, leading to boredom and disengagement. He also says it can have a negative impact on their self esteem.
His district, JEFFCO public schools, has already indicated it will not hold students back based on the READ Act.
Other districts are making plans for how they'll address retention. (Additional information posted below.)
The state will be watching to see if any more children are subject to the retention discussion, as a result of the READ Act.
In 2015, the office of literacy director says only 835 of more than 200,000 K-3 students in Colorado were retained. About 70 of them were third graders.
Some students are exempt from the provisions of the READ Act: English language learners, students with disabilities, and those who have already been held back.