If you get some new Grade 10 students just starting CAT and they’ve not had much exposure to computers, operating systems or basic concepts of ICT, then check out http://www.gcflearnfree.org/computerbasics
Don’t assume previous knowledge with learners just starting out in CAT, make sure they know the basics first!
It’s got video and text ‘lessons’ that a student can go through to get a basic grasp on the basics. I have had, in the past, students who have not had prior access to technology and I took it for granted that they already knew enough about the basics of a computer and its system.