Why is 'play' being used after 'at' here?
Native speaker’s answer
Rebecca
The term "play group" is used to mean an organised group providing care and socialization for children under five. It is a common phrase in the United Kingdom and is often used as a noun in the same way as "school", "church" or "work". Therefore "at play group" simply refers to the place that they have been. Ex: I've been at work all day. Ex: I don't want to spend more than a few hours at church. Ex: What did you do today at play group?