For RP, 15 dec is the start of holiday.. and it lasted 3 weeks
till 6 Jan. After that it's schooling term. That's why RP cannot
arrange it's Open House during the schooling term. I guess that's
the only reason why. Or perhaps RP want to be 'different'.

But surprisingly, SP, NYP, TP and NP have their Open House on
schooling terms.