It seems safe to assume that some fraction of sexually active teenagers were using condoms as their only form of birth control before the program was instituted.
It seems likely that some fraction of those will use condoms less when other forms of birth control become widely available. Among this group, this will still likely lower pregnancy rates, since condoms have a lower efficacy than other forms of birth control, but it could potentially raise STD rates.
My intuition is that the increase will be negligible, but others' intuition is different. It would be good to have some numbers on this so that we aren't guessing.
It seems likely that some fraction of those will use condoms less when other forms of birth control become widely available. Among this group, this will still likely lower pregnancy rates, since condoms have a lower efficacy than other forms of birth control, but it could potentially raise STD rates.
My intuition is that the increase will be negligible, but others' intuition is different. It would be good to have some numbers on this so that we aren't guessing.