In the poll of 1,426 children aged 14 and 15, 19 percent of youngsters reported having carried a weapon at some point in the last 12 months, with 60 per cent saying it was for protection from attack.
In the study, conducted by Portsmouth University, 20 admitted they carried a weapon to attack.
One per cent said they had them only in lessons and 5.1 per cent said they did it both inside and outside school.
Some 71 per cent felt safer in school than out.
"It provides some reassurance on the majority while raising concern over a minority," The Sun quoted Portsmouth University's Prof Carol Hayden, who led the study of Southampton pupils, as saying.