The Khan Academy and Teaching Textbooks are two examples that I know of in which the student is taught math and/or science individually, at her/his own pace via a computer. And as Sal Khan says, the student should continue improving their own skills until they have attained a mastery of the topic. Then, regardless of how long it has taken, you can advance to the next topic in the curriculum series.
This would be in opposition to the universal educational paradigm today where students are failed or moved on to the next topic (whether or not they have fully mastered this topic) because time has run out for the academic term.