DC both were diagnosed with dyslexia, (very weak memories & processing skills but high IQs) at their indie schools, while this was missed at their state schools. They were given 25% extra time in all exams & this continued at their state sixth form when they were reassessed. DD moved to another local college for year 13 where she was told because she was on a level 3 course, she didn't need the extra time or extra support! I had to fight to get DD what she deserved but in the end, DD gave up as the support she was offered was so poor.
This is just my personal opinion which shows my DC were let down more in state education; however they've also experienced fantastic dyslexia support in both sectors.