Gov. Tim Walz says coronavirus cases due to the fast-spreading omicron variant will most likely race through Minnesota’s public schools in the next few weeks now that students are back in class.

Walz told Minnesota Public Radio on Monday that school administrators across the state are right to be concerned.

He noted that modeling by the Mayo Clinic predicts a spike peaking around the third week of January, which will impact already-strained staffing.

Walz is back at work after he, his wife, and his 15-year-old son tested positive and developed mild-to-moderate symptoms in late December and spent Christmas in quarantine.