Algorithms is the unit of analysis of Computer Science. Students don't really study Computer Science until they move past elementary syntax and I/O.
The Khan Academy has extended their Computer Science curricula to address algorithms for searching, sorting, recursion and ... "BIG-O" ... which is really Big-θ, as in "Big-Theta" ... which is really a powerful way of measuring and comparing the performance of different algorithms. This opportunity for students to get a handle on Big-θ is huge. This was one of the most difficult topics that I taught, and one of the most important. Kudos to Khan Academy for adding this to their already great offering of Computer Science courses.
"We've partnered with Dartmouth college professors Tom Cormen and Devin Balkcom to teach introductory computer science algorithms, including searching, sorting, recursion, and graph theory. Learn with a combination of articles, visualizations, quizzes, and coding challenges."