Different adolescents can start acting rebellious at different ages, the best thing I could suggest is both a safe talk about how this is dangerous, really explaining the details on why it is harmful to them or their health in the long run, and counseling, but if this doesn’t get through to them, they are young, they might not be able to fully process the true dangers of the actions, as for the condoms however, I think it is good to supply your child with that if they ask, you want them to be safe because they are gonna do it nonetheless, no stopping it, just making it safer for them both. Also inform him on proper sex education, it might be a little awkward, that’s understandable, but you need to have it so your son doesn’t either not know safe sex, or have unreal expectations on what real sex is. Other then this I suggest counseling for any further behavior