Reform of math symbols for high school texts I am looking for references to papers and resources related to reforming math symbols for introductory courses at middle or high school level. Pointers to other forums also welcome.
Eidt:
For example suggesting to use $]a,b[$ for an open interval to  avoid confusion with ordered pair. Or tweaking with current symbols to make them user-friendly for a beginner.
 A: As mentioned in the comments, it would be hard to get all math teachers to agree on a common notation. Some prefer $(a,b)$ for the open interval and will probably argue vigorously for that use while others will argue that we should use $]a,b[$ for the interval. This is not just a "problem" with simple things, but there is even disagreements in advanced studies. 
The solution (IMO) is to teach the students to think abstractly. Teach the students to be comfortable with changing notation. You see this, for example, in calculus with the notation for derivative. Here we have, for example, $f'(x)$ for the derivative of a function and we have $\frac{d}{dx}f(x)$. Neither are bad or good, but work well in certain situations.
This also emphasizes the importance (IMO) that the teacher defines notation. The teacher can't assume that everyone understands that $]a,b[$ means the open interval.
All that said, you could still ask the question as to how using certain symbols and notation is related to learning. Are more symbols for example the best way to go? Or should we push towards writing down statements using words?
For this you could try to search journals for articles on: symbols, notation, mathematics, learning.
I did a quick search and found these few sources that might/might not be worth looking at:


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*Greek or not: the use of symbols and abbreviations in mathematics.(Report), The Australian mathematics teacher [0045-0685] Quinnell, Lorna yr:2012 vol:68 iss:2 pg:3

*There Is More to Mathematics than Symbols, Mathematics teaching [0025-5785] Rivera, Ferdinand yr:2010

*Notation as a tool of thought,
Iverson, Kenneth, E. Ashenhurst, Robert (Editor),
Communications of the ACM, Aug. 1980, Vol.23(8), pp.444-465 

*Using children's representations to investigate meaning-making in mathematics
Macdonald, Amy
Australasian Journal of Early Childhood, June, 2013, Vol.38(2), p.65(9)
