I actually wish there were more foreign language immersion schools. Children are language sponges and the best time to learn a language is as young as possible. Being taught in Spanish, or Mandarin, won’t prevent a child from learning English but will give the child an enormous life advantage. I say this as someone who found himself in a Spanish total immersion situation as an adult. I can get by fine but will never have the deep fluency that comes with learning a language as a child. I’m not talking about the bilingual education scam, BTW, but something else entirely.
Growing up in two or more languages, especially very different languages like English and Korean actually helps in all subjects in school. It gives you more than one pathway of thought.