[original answer by Chris Leary; tidied slightly by YC]
I am in sympathy with Kevin Buzzard's opinion that we mathematicians can become "grumpy old men." For several years (I was perhaps very naive), I labored under the belief that my students had a secondary school math background similar to mine. I have abandoned that belief. I have been at the same college now for over 25 years. I have noticed a decline in the preparation, but mostly in attitude, among our recent students. I wish I could say why this is the case, but I can't really.
As far as technology is concerned, I remember an article published in some journal on technology in math education. The article appeared during the height of the calculus reform movement in the US and was based on the authors' experiences at Oklahoma State. One of their conclusions was that, in the hands of talented students, calculators et al enhance students performance, but for less talented students, and I still remember the phrase, technology "adds one more layer of obfuscation" between the student and the material.
I believe there is something fundamentally wrong with how the US mathematics educational system functions in primary and secondary school. I don't think technology itself is the main culprit. How the technology is used is crucial.
A bigger problem is teacher preparation. My college has a school of education and the struggles of the elementary education people with mathematics are legendary. They actively resist learning anything about the math they will be teaching and only want to learn algorithms for solving problems. Even prospective secondary school teachers are not immune. A former student of mine in abstract algebra was incensed at having to learn about factoring polynomials, claiming that she was going to be a teacher, already knew how to factor, and didn't see any value in learning about polynomial rings. Unfortunately, she displayed an amazing inability to factor quadratics on an exam. So student attitudes are sometimes working against us as well.
What's wrong, and how to fix it, are not simple questions. I think there is a complex mixture here. Technology is a convenient target (and the crticism is not wholly unjustified). However, educational philosophy and policy, and societal factors, probably play a significant role as well. I'll stop here, because the more I think about these issues, the more discouraged I become.