diff --git a/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateLesson.java b/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateLesson.java
index 0436abb5132c..09e24daf3360 100644
--- a/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateLesson.java
+++ b/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateLesson.java
@@ -15,8 +15,6 @@ import icons.EducationalCoreIcons;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.List;
-
 public class CCCreateLesson extends CCCreateStudyItemActionBase {
   public static final String TITLE = "Create New " + EduNames.LESSON_TITLED;
 
@@ -82,8 +80,8 @@ public class CCCreateLesson extends CCCreateStudyItemActionBase {
   }
 
   @Override
-  protected List<? extends StudyItem> getSiblings(@NotNull Course course, @Nullable StudyItem parentItem) {
-    return course.getLessons(true);
+  protected void sortSiblings(@NotNull Course course, @Nullable StudyItem parentItem) {
+    course.sortLessons();
   }
 
   @Override
diff --git a/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateStudyItemActionBase.java b/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateStudyItemActionBase.java
index 4af27a9a372f..bad3979442b0 100644
--- a/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateStudyItemActionBase.java
+++ b/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateStudyItemActionBase.java
@@ -18,15 +18,12 @@ import com.jetbrains.edu.coursecreator.CCUtils;
 import com.jetbrains.edu.coursecreator.ui.CCCreateStudyItemDialog;
 import com.jetbrains.edu.learning.StudyTaskManager;
 import com.jetbrains.edu.learning.StudyUtils;
-import com.jetbrains.edu.learning.core.EduUtils;
 import com.jetbrains.edu.learning.courseFormat.Course;
 import com.jetbrains.edu.learning.courseFormat.StudyItem;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
-import java.util.Collections;
-import java.util.List;
 
 public abstract class CCCreateStudyItemActionBase extends DumbAwareAction {
 
@@ -103,7 +100,7 @@ public abstract class CCCreateStudyItemActionBase extends DumbAwareAction {
     CCUtils.updateHigherElements(parentDir.getVirtualFile().getChildren(), getStudyOrderable(item),
                                  item.getIndex() - 1, getItemName(), 1);
     addItem(course, item);
-    Collections.sort(getSiblings(course, parentItem), EduUtils.INDEX_COMPARATOR);
+    sortSiblings(course, parentItem);
     return createItemDir(project, item, view, parentDir, course);
   }
 
@@ -168,7 +165,7 @@ public abstract class CCCreateStudyItemActionBase extends DumbAwareAction {
                                            @NotNull final Project project,
                                            @NotNull final Course course);
 
-  protected abstract List<? extends StudyItem> getSiblings(@NotNull final Course course, @Nullable final StudyItem parentItem);
+  protected abstract void sortSiblings(@NotNull final Course course, @Nullable final StudyItem parentItem);
 
   protected abstract String getItemName();
 
diff --git a/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateTask.java b/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateTask.java
index 78e74feda957..f64e54b4a123 100644
--- a/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateTask.java
+++ b/python/educational-core/src/com/jetbrains/edu/coursecreator/actions/CCCreateTask.java
@@ -17,7 +17,6 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.Collections;
-import java.util.List;
 
 public class CCCreateTask extends CCCreateStudyItemActionBase {
   public static final String TITLE = "Create New " + EduNames.TASK_TITLED;
@@ -100,11 +99,10 @@ public class CCCreateTask extends CCCreateStudyItemActionBase {
   }
 
   @Override
-  protected List<? extends StudyItem> getSiblings(@NotNull Course course, @Nullable StudyItem parentItem) {
+  protected void sortSiblings(@NotNull Course course, @Nullable StudyItem parentItem) {
     if (parentItem instanceof Lesson) {
-      return ((Lesson)parentItem).getTaskList();
+      Collections.sort(((Lesson)parentItem).getTaskList(), EduUtils.INDEX_COMPARATOR);
     }
-    return Collections.emptyList();
   }
 
   @Override
diff --git a/python/educational-core/src/com/jetbrains/edu/coursecreator/handlers/CCLessonMoveHandlerDelegate.java b/python/educational-core/src/com/jetbrains/edu/coursecreator/handlers/CCLessonMoveHandlerDelegate.java
index 3b163cd947ca..ebe4603afc9c 100644
--- a/python/educational-core/src/com/jetbrains/edu/coursecreator/handlers/CCLessonMoveHandlerDelegate.java
+++ b/python/educational-core/src/com/jetbrains/edu/coursecreator/handlers/CCLessonMoveHandlerDelegate.java
@@ -22,14 +22,12 @@ import com.jetbrains.edu.coursecreator.CCUtils;
 import com.jetbrains.edu.coursecreator.ui.CCMoveStudyItemDialog;
 import com.jetbrains.edu.learning.StudyTaskManager;
 import com.jetbrains.edu.learning.core.EduNames;
-import com.jetbrains.edu.learning.core.EduUtils;
 import com.jetbrains.edu.learning.courseFormat.Course;
 import com.jetbrains.edu.learning.courseFormat.Lesson;
 import com.jetbrains.edu.learning.courseFormat.StudyItem;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.IOException;
-import java.util.Collections;
 
 public class CCLessonMoveHandlerDelegate extends MoveHandlerDelegate {
 
@@ -109,7 +107,7 @@ public class CCLessonMoveHandlerDelegate extends MoveHandlerDelegate {
                                  newItemIndex - 1, EduNames.LESSON, 1);
 
     sourceLesson.setIndex(newItemIndex);
-    Collections.sort(course.getLessons(true), EduUtils.INDEX_COMPARATOR);
+    course.sortLessons();
     ApplicationManager.getApplication().runWriteAction(new Runnable() {
       @Override
       public void run() {
diff --git a/python/educational-core/src/com/jetbrains/edu/learning/courseFormat/Course.java b/python/educational-core/src/com/jetbrains/edu/learning/courseFormat/Course.java
index 9e4efbe46f33..d203b338f186 100644
--- a/python/educational-core/src/com/jetbrains/edu/learning/courseFormat/Course.java
+++ b/python/educational-core/src/com/jetbrains/edu/learning/courseFormat/Course.java
@@ -44,13 +44,19 @@ public class Course {
     }
   }
 
+  /**
+   * exclude service lesson containing additional files for the course. Returns lessons copy.
+   */
   public List<Lesson> getLessons() {
     return getLessons(false);
   }
 
+  /**
+   * returns service lesson as well. Meant to be used in project generation/serialization
+   */
   public List<Lesson> getLessons(boolean withAdditional) {
-    return withAdditional ? lessons
-           : lessons.stream().filter(lesson -> !EduNames.PYCHARM_ADDITIONAL.equals(lesson.getName())).collect(Collectors.toList());
+    return withAdditional ? lessons : lessons.stream().filter(lesson -> !EduNames.PYCHARM_ADDITIONAL.equals(lesson.getName()))
+                                          .collect(Collectors.toList());
   }
 
   public void setLessons(List<Lesson> lessons) {