I took 5 years of French, 3 years of Latin. I enjoyed them up until the last ~75% or so of my senior year when I was really sick of the whole high school business. I don't think the Latin had outside utility of any sort until the 2nd or 3rd year simply because I didn't have the vocabulary (and I, like the vast majority of people, was unaware of spaced repetition and hated non-spaced repetition flashcards). The study of French and Roman culture and history was more interesting (and also fun when done in the respective languages) but due to the lack of slow history (http://unqualified-reservations.blogspot.com/2010/09/slow-hi...) in modern education I'd say its utility was limited. That utility I got from Latin the language was mainly in deciphering a few words (or contemplating a deeper meaning behind them) instead of reaching for Google's "define:word" -- but my vocabulary has lapsed and I don't care to refresh it. The other form of utility was minor because I had already studied French for two years, and that utility is contemplation of different grammatical forms and how language is structured, which can improve communication skills. I had a great English grammar class in 8th grade, and that was basically it for serious study of English grammar, but learning French allowed me to reflect more on language grammar in general so when Latin came along it was just another thing to reflect on rather than starting the reflection itself, very marginal utility.

But these utilities really don't justify the classes and resources on their own... If we want high school to produce the greatest amount of utilons, we should be explicit about that, but then many many things will need to change. I believe English should be the world language, there's no practical reason to teach anything else at the expense of other more practical things to teach (like programming), especially in English speaking countries. If we want high school to more approximate what Universities used to represent, such as encouraging more Intellectualism (which I don't think is all that great, at least society-wide, from a utility perspective...), we should be explicit about that too, and again things will change. You might want to have students study French, Greek, Latin, Lojban, etc. for at least 2 years each because of Intellectualism -- but you may also want to balance that with more modern things like deeper computer science or math or physics, which won't help most people in their future lives either but can at least be fun and intellectually interesting for people who want their Intellectualism a certain way. Or we can try for a mix, but I'd propose that our current system is a mix, and other mixes will inevitably resemble the current system by being one-size-fits-all and not work too well. So if we want both, separate. Bring back trade schools and let young teenagers wholly uninterested in purely intellectual pursuits get to doing more interesting things like building a house or building JavaEE applications, and let the intellectuals do their thing without constantly having to waste time and energy rationalizing some vague utility and relevance to their proof-carrying code research.