On a recent Tuesday evening, seven students gathered at the Dance Palace for their weekly Spanish class. During the two-hour session, not a word of English was spoken by their teacher, Laura Alderdice. Instead, Ms. Alderdice guided the class entirely in Spanish, embracing the full-immersion approach that helped her become fluent decades ago.
Following her lead, the beginner students searched for words and puzzled through verb tenses while describing what they did that day. One…