It is easy to simply imagine a second language as being a tool which may or may not come in handy in certain very specific situations. However, the benefits of having another language at your disposal may pale in comparison to actually learning one; in this case, it just might be about the journey rather than the destination. If schools were only meant to impart practical skills, why teach art, or literature, or calculus rather than how to fill out tax forms? Like any of those subjects, the study of language is more about expanding the ways that students think and view the world around them than it is about the memorization of particular facts.
Although language requirements are more common at higher levels of education, a lot of the cognitive benefits of language development are most transformative when the learner is young. By learning a second language at the same time that they learn their primary one, children will intuitively pick up on connections between words which they otherwise might not notice. A surprising number of words have roots in other languages, and knowing the backgrounds of those words can lead to a deeper understanding of them. For example, an early Spanish learner will likely add the word biblioteca, which means library. Having that knowledge will affect how they learn and understand certain English words, like ‘bibliography’ or ‘bibliophile’. In this case, knowing Spanish would help that student make the connection that all three of these words relate to books.
Beyond the etymology of individual words, other languages can show learners a new way of looking at the grammar and syntax of the English language. Other Latin-based languages like Spanish and French conjugate all of their verbs, much to the annoyance of people learning these languages. What this essentially means is that verbs are all modified based on how they are used in a sentence, similarly to how we would use the word run for the present tense, and ran for the past tense. While this seems like an unimportant and needlessly complicated step, it makes the language much more precise, and becomes easy and almost unconscious after enough practice. This forces learners to understand more obscure verb forms, such as past participle or subjunctive, and be aware of the tenses of words that they are using.
It seems reasonable to be concerned that learning two languages at once would confuse a child; having to learn and remember two words for everything, and two completely different patterns of speech simultaneously seems almost impossible. However, repeated studies such as this one by two Cornell University linguistic researchers have shown this not to be the case. Barbara Lust, a linguistics expert and director of Cornell’s Language Acquisition Lab, summed up their findings by saying “Cognitive advantages follow from becoming bilingual. These cognitive advantages can contribute to a child's future academic success."