Authorities in Niger state confirmed to the BBC that gunmen had seized an unknown number of students from the school in the town of Tegina on Sunday.
A teacher told the BBC that 150 students were missing, while other reports put the figure at about 200.
Abductions carried out for ransom are increasingly common in northern states.
In February nearly 300 girls were taken by armed men from a boarding school in Jangebe, Zamfara state. Most were later freed.
