Index: lams_tool_scratchie/src/java/org/lamsfoundation/lams/tool/scratchie/ScratchieConstants.java
===================================================================
diff -u -re5a3c4e8e88340e636c501f79cec1b91ab59a5cf -r9aa7a391a4b899f451a97e1dcb4f5cab77dea3f9
--- lams_tool_scratchie/src/java/org/lamsfoundation/lams/tool/scratchie/ScratchieConstants.java	(.../ScratchieConstants.java)	(revision e5a3c4e8e88340e636c501f79cec1b91ab59a5cf)
+++ lams_tool_scratchie/src/java/org/lamsfoundation/lams/tool/scratchie/ScratchieConstants.java	(.../ScratchieConstants.java)	(revision 9aa7a391a4b899f451a97e1dcb4f5cab77dea3f9)
@@ -152,6 +152,8 @@
     public static final String ATTR_SUBMISSION_DEADLINE = "submissionDeadline";
     
     public static final String ATTR_IS_SUBMISSION_DEADLINE_PASSED = "isSubmissionDeadlinePassed";
+    
+    public static final String ATTR_ANSWER_UIDS = "answerUids";
 
     public static final String LEARNER_MARK = "learner.mark";
     
Index: lams_tool_scratchie/src/java/org/lamsfoundation/lams/tool/scratchie/web/action/LearningAction.java
===================================================================
diff -u -r41e6a8d876e872006dce6d0f2ff540386d91649a -r9aa7a391a4b899f451a97e1dcb4f5cab77dea3f9
--- lams_tool_scratchie/src/java/org/lamsfoundation/lams/tool/scratchie/web/action/LearningAction.java	(.../LearningAction.java)	(revision 41e6a8d876e872006dce6d0f2ff540386d91649a)
+++ lams_tool_scratchie/src/java/org/lamsfoundation/lams/tool/scratchie/web/action/LearningAction.java	(.../LearningAction.java)	(revision 9aa7a391a4b899f451a97e1dcb4f5cab77dea3f9)
@@ -28,6 +28,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Date;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
@@ -100,9 +101,6 @@
 	if (param.equals("checkLeaderSubmittedNotebook")) {
 	    return checkLeaderSubmittedNotebook(mapping, form, request, response);
 	}
-	if (param.equals("isAnswerCorrect")) {
-	    return isAnswerCorrect(mapping, form, request, response);
-	}
 	if (param.equals("recordItemScratched")) {
 	    return recordItemScratched(mapping, form, request, response);
 	}
@@ -208,6 +206,16 @@
 	sessionMap.put(ScratchieConstants.ATTR_REFLECTION_ON, isReflectOnActivity);
 	sessionMap.put(ScratchieConstants.ATTR_REFLECTION_INSTRUCTION, scratchie.getReflectInstructions());
 	sessionMap.put(ScratchieConstants.ATTR_REFLECTION_ENTRY, entryText);
+	//add all answer uids to one set
+	if (isUserLeader) {
+	    Set<Long> answerUids = new HashSet<Long>();
+	    for (ScratchieItem item : (Set<ScratchieItem>)scratchie.getScratchieItems()) {
+		for (ScratchieAnswer answer : (Set<ScratchieAnswer>)item.getAnswers()) {
+		    answerUids.add(answer.getUid());
+		}
+	    }
+	    sessionMap.put(ScratchieConstants.ATTR_ANSWER_UIDS, answerUids);	    
+	}
 
 	// add define later support
 	if (scratchie.isDefineLater()) {
@@ -347,28 +355,7 @@
     }
 
     /**
-     * Return whether scratchie answer is correct or not
-     */
-    private ActionForward isAnswerCorrect(ActionMapping mapping, ActionForm form, HttpServletRequest request,
-	    HttpServletResponse response) throws JSONException, IOException {
-	initializeScratchieService();
-
-	Long answerUid = NumberUtils.createLong(request.getParameter(ScratchieConstants.PARAM_ANSWER_UID));
-	ScratchieAnswer answer = LearningAction.service.getScratchieAnswerByUid(answerUid);
-	if (answer == null) {
-	    return null;
-	}
-
-	JSONObject JSONObject = new JSONObject();
-	JSONObject.put(ScratchieConstants.ATTR_ANSWER_CORRECT, answer.isCorrect());
-	response.setContentType("application/x-json;charset=utf-8");
-	response.getWriter().print(JSONObject);
-
-	return null;
-    }
-
-    /**
-     * Record in DB that leader has scratched specified answer.
+     * Record in DB that leader has scratched specified answer. And return whether scratchie answer is correct or not
      * 
      * @throws ScratchieApplicationException
      */
@@ -378,23 +365,55 @@
 	String sessionMapID = WebUtil.readStrParam(request, ScratchieConstants.ATTR_SESSION_MAP_ID);
 	SessionMap<String, Object> sessionMap = (SessionMap<String, Object>) request.getSession().getAttribute(
 		sessionMapID);
-	final Long toolSessionId = (Long) sessionMap.get(AttributeNames.PARAM_TOOL_SESSION_ID);
+	final Long toolSessionId = (Long) sessionMap.get(AttributeNames.PARAM_TOOL_SESSION_ID);	
+	final Long answerUid = NumberUtils.createLong(request.getParameter(ScratchieConstants.PARAM_ANSWER_UID));
+	
 	ScratchieSession toolSession = LearningAction.service.getScratchieSessionBySessionId(toolSessionId);
 
 	ScratchieUser leader = this.getCurrentUser(toolSessionId);
 	// only leader is allowed to scratch answers
 	if (!toolSession.isUserGroupLeader(leader.getUid())) {
 	    return null;
 	}
+	
+	//check answer is belong to current session
+	Set<Long> answerUids = (Set<Long>) sessionMap.get(ScratchieConstants.ATTR_ANSWER_UIDS);
+	if (!answerUids.contains(answerUid)) {
+	    return null;
+	}
 
-	final Long answerUid = NumberUtils.createLong(request.getParameter(ScratchieConstants.PARAM_ANSWER_UID));
-	tryExecute(new Callable<Object>() {
+	//Return whether scratchie answer is correct or not
+	ScratchieAnswer answer = LearningAction.service.getScratchieAnswerByUid(answerUid);
+	if (answer == null) {
+	    return null;
+	}
+
+	JSONObject JSONObject = new JSONObject();
+	JSONObject.put(ScratchieConstants.ATTR_ANSWER_CORRECT, answer.isCorrect());
+	response.setContentType("application/x-json;charset=utf-8");
+	response.getWriter().print(JSONObject);
+
+	// create a new thread to record item scratched (in order to do this task in parallel not to slow down sending
+	// response back)
+	Thread recordItemScratchedThread = new Thread(new Runnable() {
 	    @Override
-	    public Object call() throws ScratchieApplicationException {
-		LearningAction.service.recordItemScratched(toolSessionId, answerUid);
-		return null;
+	    public void run() {
+
+		try {
+		    tryExecute(new Callable<Object>() {
+			@Override
+			public Object call() throws ScratchieApplicationException {
+			    LearningAction.service.recordItemScratched(toolSessionId, answerUid);
+			    return null;
+			}
+		    });
+		} catch (ScratchieApplicationException e) {
+		    log.error(e);
+		}
 	    }
-	});
+	}, "LAMS_recordItemScratched_thread");
+	recordItemScratchedThread.start();
+
 	return null;
     }
 
Index: lams_tool_scratchie/web/pages/learning/learning.jsp
===================================================================
diff -u -rc43fd06c63eb2356b9a7b068285194a2c8d52711 -r9aa7a391a4b899f451a97e1dcb4f5cab77dea3f9
--- lams_tool_scratchie/web/pages/learning/learning.jsp	(.../learning.jsp)	(revision c43fd06c63eb2356b9a7b068285194a2c8d52711)
+++ lams_tool_scratchie/web/pages/learning/learning.jsp	(.../learning.jsp)	(revision 9aa7a391a4b899f451a97e1dcb4f5cab77dea3f9)
@@ -30,11 +30,15 @@
 			var id = '-' + itemUid + '-' + answerUid;
 			
 	        $.ajax({
-	            url: '<c:url value="/learning/isAnswerCorrect.do"/>',
-	            data: 'answerUid=' + answerUid,
+	            url: '<c:url value="/learning/recordItemScratched.do"/>',
+	            data: 'sessionMapID=${sessionMapID}&answerUid=' + answerUid,
 	            dataType: 'json',
 	            type: 'post',
 	            success: function (json) {
+	            	if (json == null) {
+	            		return false;
+	            	}
+	            	
 	            	if (json.answerCorrect) {
 	            		//show animation
 	            		$('#image' + id).attr("src", "<html:rewrite page='/includes/images/scratchie-correct-animation.gif'/>?reqID=" + (new Date()).getTime());
@@ -53,13 +57,6 @@
 	            	}
 	            }
 	       	});
-	        
-	        $.ajax({
-	            url: '<c:url value="/learning/recordItemScratched.do"/>',
-	            data: 'sessionMapID=${sessionMapID}&answerUid=' + answerUid,
-	            dataType: 'json',
-	            type: 'post'
-	       	});
 		}
 
 		function finish(){