This is really a loaded question and so hard to answer. I guess instead I'd ask you these questions:
- In your area what languages are you most likely to find native speakers of so your child can meet with them directly and practice?
- Do you want your child to learn business languages (Mandarin, Japanese, German, or Portuguese)? a language that is thought of to be "pretty" like French or Italian? a language that is usefully locally (possible Spanish if you live in certain parts of the US)? or something that will help them build on other languages (like Latin or Greek)?
- What are your child's interests? If he/she likes science than German is probably the language I'd suggest. However, if he or she is more interested in arts/literature it could French/Italian/Spanish etc.
Obviously, you also need a tutor/language course instructor that works well with your kid and speaks the language well (I'm not a fan of teachers who are not native speakers, for instance...). I'd also really check with the instructors ahead of time. I visited my little sister's Spanish class one day and even though it was Spanish 3 the teacher spent most of her time explain the grammar to the kids in English. I'm someone who thinks all languages class (yes, even from day 1) should be in that respective language. I've been through classes like that and ones that weren't and you can't even compare the difference when it comes to learning the language.
Good luck with your choices! FWIW, we're a bilingual household and I'm debating teaching DD my third language but have put it on hold for the moment. It's a tricky road to navigate but I'm hoping she'll appreciate knowing at least one other language some day.
