A blog I only recently subscribed to (Physics! Blog! by Kelly O’Shea) had a very nice plug (LinReg for physics class data graphing) for a graphing program I’d not heard of before: LinReg which is available free from Pomona.
My son and I use gnuplot, which is a moderately powerful script-based graphing program that produces good graphs and has a good parameter fitting command, but I’ve given up recommending it to people, because of the extreme difficulty in installing it. It is also overkill for a lot of high school classes, where fitting a straight line is considered complicated enough.
LinReg looks like it is nearly ideal for high-school and middle school science classes. It forces students to label their axes, use units, and express the precision of their measurements. It computes error values for the intercept and slope values, using a reasonable simulation approach (sampling Gaussian distributed points about each measurement and refitting). Kelly claims that her Honors Physics students pick the program up quickly and choose to use it without prompting after the first few uses (unlike Excel, which they always see as a barrier rather than as a tool—an attitude towards spreadsheets that I share).
Data entry in LinReg seems to be mainly manual, which would be a big limitation for me even for the home-school physics class (the speed of sound lab generated several hundred data points just for the ladder measurements). Because my son and I have successfully installed and mastered gnuplot, I see no reason to change to a more limited program, but I can see the attraction of using LinReg with a class, so that less time can be spent teaching the tool and more time using it. The limited feature set looks like a very good match to most high-school science classes.