Burglars have raided the former St Helena's Grammar School in Chesterfield.
Offenders broke into the Sheffield Road building sometime between 5pm on Friday and 6.30am on Monday.
They stole some 'valuable' building equipment.
A police spokesman said: "It's possible they used a van. If you saw a van parked near the site between those times or saw any suspicious activity, please call us on 101."
The old girls' school is currently being transformed into the Chesterfield campus of the University of Derby, which is expected to open this autumn.