How long does it take to learn a language?

According to the folks at the American Center for Applied Linguistics, it takes 6 years of 100 hours a year of class time. (Paragraph below).In my view, anyone living in the US (or Canada), who plans to rely on spending the next 6 years in a classroom, twice a week, in order to improve his or her English, is probably not going to get too far.

'Extrapolating from the studies of children’s language acquisition cited below, it appears that it can take several years. For example, studies suggest that school-aged children need 2 to 3 years to develop social language (conversational skills) and 5 to 7 years to acquire the academic language proficiency needed to reach parity with native English speakers (Cummins, 1991; Thomas & Collier, 1997). Moreover, school-aged children usually attend school 5 days a week for approximately 6 hours a day, which is considerably more hours of instruction than adults in adult education programs receive. Therefore, when considering factors that affect gains in English language proficiency and other educational outcomes, it is important to keep in mind the amount of time that may be required for adults to reach the goals that are set.

McHugh, Gelatt, & Fix (2007) examined the number of instructional hours needed for the approximately 5.8 million adult lawful permanent residents currently in the United States to reach a level of proficiency necessary for civic integration or to begin post-secondary education. They found that an estimated 103 hours of study per person per year for 6 years would be necessary (600 million hours of English language instruction per year for 6 years for over 5 million immigrants). This number of instructional hours is comparable to the number provided to immigrants in other countries, such as Australia and Germany). However, the costs of implementing such a plan would be significant."