I think what is needed is something that works for high school students. If you need to do serious scientific and engineering work, programs like Matlab and gnu

I think what is needed is something that works for high school students. If you need to do serious scientific and engineering work, programs like Matlab and gnuplot, which you mentioned, work, and even learning Python will probably give better results than an old graphing calculator that isn't high-precision. As was suggested in the article, a cheap Chromebook is very well capable of running Python, and cheap linux laptops could run Matlab.