Hi all, is it a concern that our kid won't pick up English from preschool cos we are not speaking English but mostly Mandarin at home?

Agree with Samantha. To get them to pick up a language, they need to be speaking it regularly. Do speak to them in English as well at home! If it is hard to have one parent converse in English and the other in Chinese, choose "English days" and "Mandarin days". Example, Mon, Wed, Fri, Sun the family speaks English and tues, Thurs, Sat Mandarin! :)