For educational use there are numerous special Linux's available, they include ADIOS, Skolelinux, Edubuntu, kmlinux, and so on.
Of course Mandriva is a good choice, but there is special stuff for schools. You may want to look at
www.distrowatch.com and use their search function for details. Search for educational software.
We are open-source fans and believe in free software. As dexter11 pointed out, it is really free, no strings attached. Free as the spoken word, free as using the alphabet, free to be copied and passed-on legally!
Welcome to the world of free open-source and properly working software! If at some point in the future you feel you could contribute by developing software, good for you!