Hang on.
If you were having a conversation with someone, and someone walked up and interrupted you'd think they were SO rude. Same as if the person you were talking to suddenly started ignoring you, and talking TO the person who interrupted you.
Dunno about you lot, but i was always taught it's rude to interrupt a conversation, and i've always taught my kids the same thing.
So no, i wouldn't drop a conversation with anyone to pay attention to my kids, and strangely enough, at pick up, i'm perfectly capable of giving my kids a hug/kiss on the cheek and hold their hand to give it a squeeze without missing a beat in my conversation, to acknowledge them and then when it IS ok to break, pay attention to them then.
I don't need some school teacher twat telling me i'm emotionally stunting my kids by not giving them my immediate, undivided attention the minute they breathe in my vicinity.