Can someone please tell me what type of rash this is? It's on his behind, itches like crazy. I've…

Can someone please tell me what type of rash this is? It's on his behind, itches like crazy. I've been putting calamine lotion but don't see improvement. His school sent a letter hime a few weeks ago about someone in the class having ring worm. Hope and pray to the lord it is not. I've never experienced or seen ringworm before and it's not a exact ring. It's a tad bit red cause he wouldn't stop scratching. Pediatrician is closed, maybe urgent care problem??