Five elementary school students were injured Tuesday morning when a truck driven by a farmer hit them on National Route 377 in Onohara, Kagawa Prefecture, police said.
Kiyotaka Ishikawa and Kazuya Inoshita, both 8, were seriously injured.
The other three boys suffered minor injuries, police said.
The driver, Yoshio Inoue, 57, was arrested on suspicion of negligence.
Comments from Inoue and police investigators suggest he was trying to avoid a car coming in the opposite direction when he struck the boys, who were walking in line on their way to school at around 7:30 a.m.
The road the accident occurred on has no sidewalk.