  Introducing Modern Physics represents an increasingly urgent need, towards
which physics education concentrates many efforts. In order to contribute to
this attempt, at the Department of Mathematics and Physics of Roma Tre
University in Rome we focused on the possibility of treating General Relativity
(GR) at high school level. We started with an interactive activity addressed to
students that exploits the rubber sheet analogy (RSA) to show various phenomena
related to gravity using the concept of space-time. Then, having verified its
effectiveness, we began to include it among the initiatives the Department
carry for high school teacher professional development, with the explicit aim
of making them capable of carrying on the activity autonomously in the
classrooms. In this paper, we analyse the teacher training approach we
realized, and all the materials developed.
