How do I help a 10 year old child cope with the death his school teacher?

Simple is best. The 10yo's past experience with pets or bugs gives them a basic understanding of the physical reality of death. Since their thinking processes won't begin to embrace advanced thinking until well into the teens, you need to stay with simple. Instead of trying to provide an elaborate discussion of heaven or eternal love, provide an open invitation to ask questions. Kids will come back again & again.