The likes of Remi Streete, Bradden Inman and Conor Newton have impressed the Argentine.
"They have a great future ahead of them but they have to learn, they have to be clever," Jonas told nufc.co.uk.
"There is a good opportunity for them here at Newcastle. I wish that when I was their age I was at a club like this one with these chances.
"Players do not always have this opportunity and they should realise how lucky they are.
"They are young and they have to focus on football. They have to learn and to train hard, showing the manager that they can play.
"If they can do that, they are going to be in the squad and will have more and more opportunities."