You appear to be totally missing the points here.
Nonsense. Johnson ATTENDED at least several of those parties,
It has yet to be clarified which were parties (if any) or whether they were all 'work related meetings'.
and a large number of them occurred in his house!
There don't seem to be a large number of them having occurred in his place of residence (The 'flat' above No 10). It seems a large number occurred in his 'place of work'.

And no, I haven't worked in a large secondary school. Does that have any bearing? Or have you worked there and have your own knowledge of such goings on?