Emergency personnel work at the scene following a drone attack in the town of Rzhyshchiv, Kyiv region, Ukraine, Wednesday, March 22, 2023. AP
The emergency services initially said three people had been killed in the strike south of the capital Kyiv but police later announced another victim.
"The fourth victim was a 40-year-old driver. The man did not go down to the shelter during the air raid alerts," said Andrii Nebytov, the head of the Kyiv region police.
An ambulance driver called to the scene was among those killed, the office of Ukraine's prosecutor general said.
The strike hit a high school about 80 kilometres (50 miles) south of Kyiv, said the emergency services, which published images of badly damaged buildings.
The attack "partially destroyed" two floors of two student residences and a building that is used for studying, the same source said.
A fire affecting more than 300 square metres (3,200 square feet) of the school was extinguished shortly before 7 am local time, according to the emergency services.
Ukraine's air force said Russia attacked Ukraine with 21 "Iranian-made" drones, with 16 shot down.
"Over 20 Iranian murderous drones, plus missiles, numerous shelling... and that's just in one night of Russian terror against Ukraine," President Volodymyr Zelensky said on Twitter.
Russia regularly pounds Ukraine with missiles, artillery and drones, often causing power cuts that prevent people from warming their homes or getting drinking water.