No, mocks are not moderated, generally the grade boundaries from the previous year are used. This is usually accurate. However this year, we don't know how the change in specification for chemistry and the added practical and maths content will change the exams.
In terms of teaching, it is much the same, apart from the way we record practical work. However I would describe the examinations as a little chaotic because we truly don't know what they will be like. The specimen papers are really tough. We are hoping that the grade boundaries will be lowered to match with the distribution.
Chemistry is tough. PP are correct in saying that maths, physics etc are not easy either. However, students are not usually prepared for the depth of knowledge required, the mathematical understanding or the ability to just memorise things like reaction mechanisms. It has come as a shock to a lot of our students.