Parents are being advised by schools to check their children's phones in light of a social media trend they say is creating an "arbitrary rivalry" and encouraging violence between pupils.
Posts circulating on platforms such as TikTok and Snapchat have divided schools into "red" and "blue" categories, referencing a "Bristol War" for pupils in Years 7, 8, 9 and 10.
Avon and Somerset Police said it would be carrying out reassurance patrols in Bristol as a "precaution" and added it was "monitoring the situation extremely closely".
The force said there was no evidence to suggest any incidents linked to the "national" social media trend had occurred in the city.
Ch Insp Keith Smith said he understood the posts would "cause concern to communities".
