Stand-off Louis Senter and full-back Gregor Ramsay come in from Easterhouse Panthers, while hooker Lewis Clarke and half-back Finn Murphy link up from Edinburgh Eagles.
Senter, whose father has been a major figure in Scotland RL for the last decade or more, has spent time at the Hull KR academy, and has been scoring tries from centre for Halifax’s reserve team this season.
Ramsay hails from Alloa, Clarke from Bonnyrigg, and Murphy is currently a student at St Andrews University, and shone at the Commonwealth Championship.
Coach Steve McCormack said: “Bringing these lads in will do them the world of good.
“They will get the chance to see the likes of Danny Brough, Ben Kavanagh, Joe Wardle etc. – top Super League players – close up and learn from them. We did this with Davie Scott three years ago and look how far he’s come since then.
“Hopefully these lads will do the same. Louis has shown he can cope with a step up in rugby this season and one or two of these lads could make the final squad.”
Winger or full-back Scott, from Stirling, converted to league at Easterhouse Panthers and is now a regular for Doncaster in the Championship and played for Scotland in the World Cup quarter-final against New Zealand 11 months ago.
Scotland will announce their final 20-man squad on Tuesday ahead of the Wales game at Workington’s Derwent Park on Friday night. Those youngsters not selected for the senior team will return to the Under-19s to play Ireland (in Dublin on 25 October) and England (1 November at University of Edinburgh).