Sorry, I only read the first page of this topic but I read this and these bits here are exactly what I think. For my experience, I was taught with red pens and Xs, circles, notes and question marks... or the dreaded 'see me' especially in Maths. Im not bad at maths, but I was very unwell in my first school so missed a lot of the basics, so I had to cobble together a lot of the patterns to make the more advanced stuff make sense. Sometimes this went horribly wrong and I hated feeling like Id let people down or failure in a lesson was the worst thing that could happen (this was through my parents rather than the school, my dad was an ex-headteacher and I was petrified of him until I was about 14, and my mum never questioned him) so my books were usually stained with tears as well as red pen. It wasnt until secondary school I got a teacher that understood why I was they way I was and built my confidence around maths, and I was soon jumping up ability classes into the one just below top. I dont think the colour of pen or using an X makes much difference, it's how you are taught and how you are brought up.