Soca is a Caribbean music genre, a fast and high-energy descendant of calypso, central to Trinidad Carnival. If your kid is into soca they are into Caribbean music, often around Notting Hill Carnival in the UK. Not concerning. The name is a contraction of "soul of calypso." If your kid uses it constantly, ask them where they first heard it, not to police their speech but to understand which online community they are in.