I will be teaching an introductory statistics course to gifted middle-school students over the course 3ish weeks. I'll have about 90 contact hours with the students. Any recommendations on a concise textbook that covers the basics? I would certainly prefer it be low-cost.
I used to recommend Jessica Utts' "Seeing Through Statistics" as a supplementary, not-so-technical reading about statistics to my undergraduate students. You might want to request a copy to review and see if it is appropriate for your kids. (I am saying "I used to" because I don't teach at a university anymore.)
This book motivates statistics by several real life data-based stories (case studies) in the intro chapters (Does aspirin prevent heart attacks? Is it the heart or hypothalamus that is responsible for our emotions? Would Lee Iaccoca beat George Bush in Republican primaries? Do matching wrong answers on a test provide enough evidence of cheating? Do women suffer from worse hangovers than men? and a bunch of others), and then returns to these examples when the appropriate statistical tools are being developed (randomized controlled trials for aspirin; outlier graphs and diagnostics for the cheating example -- the answers turned out to be clustered according to the country of origin, and other test takers from the same country provided the same "wrong" answers; etc.). The math requirements are pretty light, and everything is done at algebra level. There first six or so chapters don't have any formulae at all, or at least I did not stumble upon any in Amazon preview.
I think Jessica Utts' statistics books, and generally her efforts on statistics education front, made her famous enough to be propelled into the position of the President of the American Statistical Association (the 2016 term). I cannot think of any higher professional honor. (I said "I think" because I cannot speak for the other 10,000 statisticians who voted for her.)