NEW YORK (CBSNewYork) – Mayor Bill de Blasio is saying use it or lose it to parents of public school students registered for in-person learning.

“These seats are precious kids need these seats, a seat should not go unutilized,” de Blasio said. “If your child doesn’t show up next week, we’re saying to you we’re about to move your child into remote, unless you have a specific excuse or you make clear to us what’s going on.”

Watch: Mayor Bill de Blasio Discusses School Reopenings

Starting Monday, school buildings reopen for 3-K through fifth grade students.

More: Mayor De Blasio Announces Phased Reopening Plan For NYC Public Schools; Elementary, Pre-K To Reopen Dec. 7

District 75 students return next Thursday.

Mayor de Blasio says education officials need an accurate count as schools prepare for students to return to classrooms five days a week where possible.

Before kids can return, parents are required to sign a testing consent form or have a proper medical exemption.