<p>The colleges generally recommend four years of a single language; four years actually refer to the level achieved, not the number of years one spent learning the language. For example, S started Spanish in 7th grade. But of all his classmates, he was one of only two who went straight into Spanish 3 in 9th grade; the rest went either into Spanish 1 or Spanish 2. As far as colleges were concerned, these classmates had to spend all four high school years in Spanish to be considered to have taken four years in Spanish. They could not claim, having taken Spanish from 7th grade through 10th grade, to have had four years of Spanish. That’s not how it works.
Having said this, four years is a recommendation, not a requirement. What I am trying to say is that high school level Mandarin for two years will not sound any more impressive than high school level French for two years. If the student is interested in Chinese studies, it will be taken as a sign of interest and will be a plus. But it won’t be of significance for someone interested in engineering.</p>