order assignments by time

app/controllers/assignments_controller.rb

@@ -4,7 +4,7 @@ class AssignmentsController < ApplicationController
   before_action :set_session, :set_users
 
   def index
-    @assignments = Assignment.all
+    @assignments = Assignment.all.joins(:session, :user).order('sessions.starts_at')
     if params[:user_id]
       @assignments = @assignments.where(user_id: params[:user_id])
     end