Infancy (0-3 years) represents a unique time for language learning. Previous research shows that infants' second language (L2) learning advances rapidly in early education centers, through a research-based method and curriculum delivered by native-speaking language tutors. Here we test the potential of this method for broad application, through an interactive online tool, SparkLing™, which trains and certifies language tutors to implement the program in infant education centers. Intervention infants (n = 168) from families of predominantly low socioeconomic status (SES) backgrounds in Madrid, Spain, experienced 18 or 36 weeks of L2 (English) exposure, through daily, 45-min, group sessions led by SparkLing™-trained tutors and were compared to a matched Current Practice Comparison (CPC) group of peers (n = 72). Intervention children outperformed the CPC group and showed rapid gains in English comprehension and production. SES was not a significant factor in learning. Infants' L2 skills advance quickly using this research-to-practice, scalable program for play-based infant L2 instruction.