diff --git a/hourglass/server/main.js b/hourglass/server/main.js
index aabb5c7..115579b 100644
--- a/hourglass/server/main.js
+++ b/hourglass/server/main.js
@@ -52,7 +52,7 @@ Meteor.methods({
   },
   'joinClass': function(change, pass) {
     found = classes.find({_id: change, status: true}).fetch();
-    if (Meteor.user() != null && found.length > 0 && pass === found[0].code) {
+    if (Meteor.user() != null && found.length > 0 && pass === found[0].code && Meteor.user().profile.classes.indexOf(change) === -1) {
       current = Meteor.user().profile;
       current.classes.append(change);
       Meteor.users.update({_id: Meteor.userId()}, {$set: {profile: current}});
@@ -60,5 +60,17 @@ Meteor.methods({
     } else {
       return 0;
     }
+  },
+  'leaveClass': function(change) {
+    if (Meteor.user() != null) {
+      profile = Meteor.user().profile
+      index = profile.classes.indexOf(change)
+      if (index >= 0) {
+        profile.classes.splice(index, 1);
+        Meteor.users.update({_id: Meteor.userId()}, {$set: {profile: current}});
+        return 1
+      }
+
+    }
   }
 });
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