I totally agree with your opinion. We should really take into consideration the number of S6 classes provided compared with the number of S5 classes. Next the ratio of S5 Science and Arts classes will also affect the admission of S6 since there might be 3 Science classes and 2 Art classes in S5 but in S6 might be 2 Science classes and 1 Art classes which may affect the admission of S6 Art classes as the no doubt there will not be any spaces left in S6 Science class but there might be few places left in S6 classes.