Well - It can be blended together since both topics applies to each other but however - IMO - It should be kept as a separate issue because Sex Education involves a lot more exploration such as knowing about the diseases, sexual health, safety, and sexual wellness. Abstinence only applies to being "resisted" upon if one were to taught about it. Just saying. 
As for moral value related to sexual issues - How can it be taught when even us adults get it mixed up too? What I mean is - Everyone has their own different views when it comes to moral values. That is why it is best to acquire it much later when you are an adult rather than when you are a teenager.
