Dd is in the same boat. RE has always been compulsory but taught in an hour a week. With the new GCSE the school has just continued that policy but is now trying to cram a full, very content heavy subject into that one hour. Also her teacher was off for four months in year 10.
I think the school have been very slow to react and adapt. They will no doubt realise in August when a whole cohort come out with 1s, 2s and 3s.
The other thing is that the handful of kids who might have actually wanted to take the new GCSE have been forced to spend one hour a week with a disengaged difficult class of 30+.
Dd has done no work at all for RS and her revision plan has her doing two hours the weekend before. If she gets a 4 it will be a miracle but unfortunately we don't believe in miracles in our house 