Public schools...
Reading, writing and math.
Foreign languages are a nice elective I suppose.
The most important subject aside from those three mentioned above:
History no doubt in my mind.
You know history you can see the future.
There is nothing new under the sun, IMO.

The reason why I chose 4 languages should be evident to you, JRH, unless you are dumber than I was inclined to believe.

Chinese (1 Billion Plus Chinese)
Hindu (1 Billion plus Indians)
Japanese (130 Million Japanese, the largest investor group in the United States, outside of Great Britain which speaks English)
German (Another major economic power)

To mention the others is to ignore the fact that in just those four languages any one can easily approach Over half the population of the World, including the two fastest growing populations and communicate. Your mention of the romance languages fails to account for the fact that Europe is in decline and will not likely be of any great influence in the next 50 years outside of Germany which remains the world's largest exporter.

But if we are going to argue about languages, then we can ditch everything but English, as it has become the universal language of science, engineering and technology.

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Libertas inaestimabilis res est - Liberty is a thing beyond all price. | Sic Semper Tyrannis