Are you referring to Standards Documents 30 & 31 which list current RTFs and ATOs? If yes then if a school isn't listed there then they might instead be listed here as a DTO (a new training organisation entity that all RTFs must become by April 2019):
https://www.caa.co.uk/General-aviati...Organisations/ . If not then they might not have made it onto the list yet if it hasn't been updated for a few weeks (no idea how often the CAA updates it). Perhaps give the school a call and ask them?