Research shows that condom availability does not increase sexual activity. Nor does making condoms less accessible decrease sexual activity.
School Condom Availability
Condom Availability Programs in U.S. Schools
It seems that pediatricians agree that condoms should be made available in schools.
Condom Use by Adolescents
It makes sense. There is no research showing an increase in sexual activity within those schools that have condoms available/more available than schools that don't.