education – Best suited Wolfram tool for a high school student

My daughter is a high school student and she likes science. In a couple of years she will go to university. I had a look at the Wolfram products (I used myself Mathematica when I was young) but I was unable to figure out what could be best suited for a student like her who is starting do some non trivial mathematics and physics. There are many tools, some looking very similar. Any suggestion? Can we start with something free?
Thanks for any help!