I understand that doubt. I don't entirely trust studies either. Just out of curiosity, did you also take advantage of any music classes? I did both the foreign language and played violin and piano and was a straight A student. I never excelled in either foreign language or music, but I've never been sorry I took those classes.
If a program is available why not take advantage of it if it will help your child to be well-rounded.
I was almost a straight A student for all four years and also took music and even achieved the highest award in music possible at graduation for my work in music, would have been valedictorian if it wasn't for the D I got in French studies. I was just not into it. Felt it was useless but since it was mandatory, had to take it. My beef is that language classes should be an elective or pushed to college, not be made mandatory in high school. And for the asshats that think I'm anti-spanish, this is about ALL language classes, not just spanish.