I have been using NCSS in my high school class room for 22 years. I find it very easy to use and my students use it to calculate their results for their lab reports, science fair projects, and now they are using it for AP Research projects. It can be used for everything from the basics to the most advanced statistics. NCSS is very affordable for any high school budget.
I am a very satisfied user of NCSS. For years I used SPSS in my consulting work, but the cost got to be exorbitant. When I started using NCSS, I found it easy and intuitive to use and extremely accurate in its results. It is not only my statistical analysis program of choice but I have recommended it to many of my clients as well. When I've had questions and called NCSS, I have always gotten expert help and advice and never had a problem go unsolved. Keep up the good work.