The younger a student is for his or her grade, the more likely it is that they will be diagnosed with a learning disability in their earliest school years, according to a new study by the city's Independent Budget Office, which examined the records of 290,000 public school students.

Supervising Analyst Sarita Subramanian says they started looking at the youngest students in kindergarten through third grade from the 2017-18 school year by birth month to see what share of students were classified with a disability.  

They found that 22.7 percent of students born in November and 23.1 percent born in December were classified as having a learning disability, compared to 16.5 percent of those born in January and 16.8 percent born in February.

Other studies have found that birth month matters the most in the youngest grades because that's when development largely happens.

The city's public schools require that children who turn 5 years old by December 31 must go to kindergarten. It's one of the latest cutoff dates in the nation. It means that many students must enter kindergarten when they are four. Some experts say that puts them at a disadvantage compared to students well past five and a half years old.

The new study suggests that the city might be classifying some children as having learning disabilities when the issue might be they are simply too young to enter kindergarten.

“Special education assessments and eligibility decisions are based on the needs of each individual student, and teachers differentiate instruction by student to meet everyone’s needs,” the Department of Education said in a statement.

The Education Department added that it will review the findings and data to see how they can best be used.