Castleford Head of Youth Development Steve Gill said: “This is an ideal opportunity for both players to gain valuable experience in a first team environment.
“Considering Jordan could still play in our under 18’s competition this year and John is only a few months over the deadline, we feel playing first team in Championship 1 is a good step for them both at this point in their development.”
Thompson and Davies will continue to train full time with the Tigers first team squad, and join the City Knights late on in the week for team running sessions.
Tigers head coach Terry Matterson said: “I’m pleased the boys are hooking up with York. They have got a quality coach in Chris Thorman.
“I’m happy that we can call them back when needed and it will prove an important part of their development.”