A record number of city schools are packing too many kids into classrooms, according to a new report.

Based on a survey of registers for the first few weeks of this school year, the United Federation of Teachers (UFT) found that nearly 700 schools have oversized classes, affecting almost 250,000 students citywide.

The UFT negotiated maximum class sizes in their contract and those sizes vary based on grade level. In Brooklyn, Sheepshead Bay High School and I.S. 318 were found to have the most overcrowded classes.

Experts say oversized classes can translate into lower standardized test scores, a shortage of supplies and an unbalanced number of students to teachers. Many students, parents and teachers have rallied over the issue in attempt to stop the Department of Education (DOE) from merging schools together.