diff --git a/advlabdb/customClasses.py b/advlabdb/customClasses.py
index 971d1ff..d2e8801 100644
--- a/advlabdb/customClasses.py
+++ b/advlabdb/customClasses.py
@@ -1,7 +1,9 @@
 from flask_admin import AdminIndexView
 from flask_admin.contrib.sqla import ModelView
 from flask_security import current_user
-from flask import redirect, request, url_for
+from flask import redirect, request, url_for, flash
+
+from advlabdb.exceptions import ModelViewValidatorException
 
 
 def adminViewIsAccessible():
@@ -49,3 +51,10 @@ class SecureModelView(ModelView):
             return super().get_count_query().filter(self.queryFilter())
         else:
             return super().get_count_query()
+
+    def handle_view_exception(self, exc):
+        if type(exc) == ModelViewValidatorException:
+            flash(str(exc), "error")
+            return True
+
+        return super().handle_view_exception(exc)
diff --git a/advlabdb/exceptions.py b/advlabdb/exceptions.py
new file mode 100644
index 0000000..da95330
--- /dev/null
+++ b/advlabdb/exceptions.py
@@ -0,0 +1,2 @@
+class ModelViewValidatorException(Exception):
+    pass
diff --git a/advlabdb/modelViews.py b/advlabdb/modelViews.py
index ff926f8..e69dbcd 100644
--- a/advlabdb/modelViews.py
+++ b/advlabdb/modelViews.py
@@ -34,6 +34,7 @@ from advlabdb.utils import (
     setUserActiveSemester,
     userActiveSemester,
 )
+from advlabdb.exceptions import ModelViewValidatorException
 
 
 class UserView(SecureModelView):
@@ -49,9 +50,6 @@ class UserView(SecureModelView):
         "roles": {"validators": [DataRequired(message="A role is required!")]},
     }
 
-    deleteSelfException = "Tried to delete yourself as user!"
-    deactivateSelfException = "Tried to deactiavte yourself as user!"
-
     def create_model(self, form):
         password = randomPassword()
         passwordHash = hash_password(password)
@@ -81,17 +79,11 @@ class UserView(SecureModelView):
 
     def on_model_delete(self, model):
         if model == current_user:
-            raise Exception(self.deleteSelfException)
+            raise ModelViewValidatorException("Tried to delete yourself as user!")
 
     def on_model_change(self, form, model, is_created):
         if model == current_user and not form.active.data:
-            raise Exception(self.deactivateSelfException)
-
-    def handle_view_exception(self, exc):
-        if exc.args[0] in (self.deleteSelfException, self.deactivateSelfException):
-            pass
-        else:
-            return super().handle_view_exception(exc)
+            raise ModelViewValidatorException("Tried to deactiavte yourself as user!")
 
 
 class RoleView(SecureModelView):
@@ -261,8 +253,6 @@ class PartStudentView(SecureModelView):
 
     column_filters = ["part", "student", "group"]
 
-    partGroupPartMismatchException = "Student's part and group's part do not match!"
-
     def queryFilter(self):
         return PartStudent.part_id.in_([part.id for part in userActiveSemester().parts])
 
@@ -272,13 +262,7 @@ class PartStudentView(SecureModelView):
 
     def on_model_change(self, form, model, is_created):
         if model.group and model.part != model.group.part:
-            raise Exception(self.partGroupPartMismatchException)
-
-    def handle_view_exception(self, exc):
-        if exc.args[0] in (self.partGroupPartMismatchException):
-            pass
-        else:
-            return super().handle_view_exception(exc)
+            raise ModelViewValidatorException("Student's part and group's part do not match!")
 
     def update_model(self, form, model):
         if form.final_part_mark.data == -1:
@@ -310,8 +294,6 @@ class GroupView(SecureModelView):
     column_list = ["number", "part", "part_students", "group_experiments"]
     column_filters = ["number", "part"]
 
-    partStudentPartPartMismatchException = "Group's part and student's part do not match!"
-
     def queryFilter(self):
         return Group.part_id.in_([part.id for part in userActiveSemester().parts])
 
@@ -333,13 +315,7 @@ class GroupView(SecureModelView):
     def on_model_change(self, form, model, is_created):
         for partStudent in model.part_students:
             if model.part != partStudent.part:
-                raise Exception(self.partStudentPartPartMismatchException)
-
-    def handle_view_exception(self, exc):
-        if exc.args[0] in (self.partStudentPartPartMismatchException):
-            pass
-        else:
-            return super().handle_view_exception(exc)
+                raise ModelViewValidatorException("Group's part and student's part do not match!")
 
     def create_form(self, obj=None):
         form = self.CreateForm
diff --git a/advlabdb/models.py b/advlabdb/models.py
index 7b44fc0..8d4e067 100644
--- a/advlabdb/models.py
+++ b/advlabdb/models.py
@@ -131,9 +131,18 @@ class Experiment(db.Model):
     responsibility = db.Column(db.String(200), nullable=True)
     duration_in_days = db.Column(db.Integer, db.CheckConstraint("duration_in_days > -1"), nullable=False)
     active = db.Column(db.Boolean, default=True, nullable=False)
-    oral_weighting = db.Column(db.Float, nullable=False)
-    protocol_weighting = db.Column(db.Float, nullable=False)
-    final_weighting = db.Column(db.Float, nullable=False)
+    oral_weighting = db.Column(
+        db.Float, db.CheckConstraint("oral_weighting >= 0"), db.CheckConstraint("oral_weighting <= 1"), nullable=False
+    )
+    protocol_weighting = db.Column(
+        db.Float,
+        db.CheckConstraint("protocol_weighting >= 0"),
+        db.CheckConstraint("protocol_weighting <= 1"),
+        nullable=False,
+    )
+    final_weighting = db.Column(
+        db.Float, db.CheckConstraint("final_weighting >= 0"), db.CheckConstraint("final_weightin <= 1"), nullable=False
+    )
     semester_experiments = db.relationship("SemesterExperiment", backref="experiment", lazy=True)
 
     def repr(self):