I feel it is important that students find their own way through a problem. It is during the sharing time, either with a partner, small group or the whole class, where students are exposed to other ways of thinking about a problem. If a student's problem solving is inefficient, but still gets her the correct answer, she may be unwilling to try something else until she feels secure with another, more efficient way. This requires time and lots of experience. During our sharing time, we talk about the different strategies (I record on chart paper and post around the room so they are visible side by side) and the pros and cons of each. The students will often point out the ones that are ineffecient and full of pitfalls. I find that pairing students carefully at times will help a child who is struggling move to a more efficient stategy. However, it will come only when the child feels comfortable and understands. For some students, that really takes time.