// Snippet from Template
{{#each elements}}
{{> post-element this}}
{{/each}}
// Snippet from Client
M
You didn't posted your template helper code.
When you do return Posts.find() from the helper function, the query should also contain the sort arguments, like as below:
Template.myTemplate.elements = function(){
Meteor.subscribe('thePosts');
return Posts.find({}, {sort:{createdAt:-1}, reactive:true});
}