For
It prevents delayed speech and language mixing.
Against
Children can naturally learn multiple languages.
Anonymous excerpts, translated where noted.
“Anecdotal but all the bi-lingual kids I know, including my daughter, were late.”
“It's actually very typical for multilingual children to start producing language later than monolingual children.”
“No, this is a myth.”
“Speaking multiple languages is one of the best things you can do for your children!”