diff --git a/src/interface/generic/eduUnit.ts b/src/interface/generic/eduUnit.ts
index 3995240..69526f6 100644
--- a/src/interface/generic/eduUnit.ts
+++ b/src/interface/generic/eduUnit.ts
@@ -12,4 +12,10 @@ export interface EducationalUnit {
 	 * The planned lessons are used to represent the substitution plan.
 	 */
 	plannedLessons: PlannedLesson[];
+
+	/**
+	 * The type of the educational unit.
+	 * The type can be "schoolClass", "room", or "teacher".
+	 */
+	type: 'schoolClass' | 'room' | 'teacher';
 }
diff --git a/src/interface/index.ts b/src/interface/index.ts
index e7b750d..7c1f3d7 100644
--- a/src/interface/index.ts
+++ b/src/interface/index.ts
@@ -1,4 +1,5 @@
 import { Course } from './course';
+import { EducationalUnit } from './generic/eduUnit';
 import { Lesson } from './lesson';
 import { PlannedLesson } from './plannedLesson';
 import { Room } from './room';
@@ -8,6 +9,7 @@ import { Teacher } from './teacher';
 
 export type {
 	Course,
+	EducationalUnit,
 	ISubstitutionPlan,
 	Lesson,
 	PlannedLesson,
diff --git a/src/interface/room.ts b/src/interface/room.ts
index ab8487a..94e5425 100644
--- a/src/interface/room.ts
+++ b/src/interface/room.ts
@@ -3,4 +3,6 @@ import { EducationalUnit } from './generic/eduUnit.js';
 /**
  * A room represents a room in a school, which is used in the timetable.
  */
-export interface Room extends EducationalUnit {}
+export interface Room extends EducationalUnit {
+	readonly type: 'room';
+}
diff --git a/src/interface/schoolclass.ts b/src/interface/schoolclass.ts
index 6cd2b57..1cb227e 100644
--- a/src/interface/schoolclass.ts
+++ b/src/interface/schoolclass.ts
@@ -6,6 +6,8 @@ import { Lesson } from './lesson.js';
  * A school class represents a classical class or course in a school.
  */
 export interface SchoolClass extends EducationalUnit {
+	readonly type: 'schoolClass';
+
 	/**
 	 * The timetable of the school class.
 	 * It is a merge of all lessons and courses, where all courses get an id of `-1`.
diff --git a/src/interface/teacher.ts b/src/interface/teacher.ts
index bf778a8..0a8cbda 100644
--- a/src/interface/teacher.ts
+++ b/src/interface/teacher.ts
@@ -3,4 +3,6 @@ import { EducationalUnit } from './generic/eduUnit.js';
 /**
  * A teacher represents a teacher in a school (obviously -_-).
  */
-export interface Teacher extends EducationalUnit {}
+export interface Teacher extends EducationalUnit {
+	readonly type: 'teacher';
+}
diff --git a/src/parser/schoolClass.ts b/src/parser/schoolClass.ts
index cf622fb..452f35d 100644
--- a/src/parser/schoolClass.ts
+++ b/src/parser/schoolClass.ts
@@ -40,6 +40,7 @@ export class SchoolClassParser implements IndiwareParser<SchoolClass> {
 
 		return {
 			name: `${xml.Kurz}`,
+			type: 'schoolClass',
 			timetable,
 			courses,
 			lessons,
diff --git a/src/parser/substitutionPlan.ts b/src/parser/substitutionPlan.ts
index 582bb2d..7061af8 100644
--- a/src/parser/substitutionPlan.ts
+++ b/src/parser/substitutionPlan.ts
@@ -37,6 +37,7 @@ export class SubstitutionPlanParser implements IndiwareParser<SubstitutionPlan>
 						rooms.push({
 							name: lesson.room.value,
 							plannedLessons: [lesson],
+							type: 'room',
 						});
 					}
 				}
@@ -51,6 +52,7 @@ export class SubstitutionPlanParser implements IndiwareParser<SubstitutionPlan>
 							teachers.push({
 								name: teacher,
 								plannedLessons: [lesson],
+								type: 'teacher',
 							});
 						}
 					}