These are just two "implantations" of the same "etablissement" with different grades offered, different address and possibly different contacts. Physical school sites tend to have one or more "implantations" from one or more "etablissement". It is OK to map the "etablissement" as a site relation as extra information, but that makes things very complicated and it has not much added value for data users. It is however never a good idea to NOT map the individual implantations.