--- a/ucs-school-4.1r2/ucs-school-import/usr/share/ucs-school-import/scripts/ucs-school-import	
+++ a/ucs-school-4.1r2/ucs-school-import/usr/share/ucs-school-import/scripts/ucs-school-import	
@@ -1764,16 +1764,21 @@ def create_network(schoolNr, network, iprange=None, defaultrouter=None, nameserv
 		pass
 
 	position.setDn("cn=%s,cn=dhcp,%s" % (schoolNr.lower(), getDN(schoolNr)))
-	object = dhcp_service_module.object(co, lo, position=position, superordinate=superordinate)
-	object = dhcp_subnet_module.object(co, lo, position=position, superordinate=dhcp_subnet_module)
-	object.open()
-	object['subnet'] = str(network.network)
-	object['subnetmask'] = str(network.netmask)
-	object['broadcastaddress'] = str(network.broadcast)
-	try:
-		create_object(object, ignore_exists=True)
-	except:
+	dhcp_service_objects = univention.admin.modules.lookup(
+		dhcp_service_module, co, lo, scope='sub', superordinate=superordinate,
+		base=baseDN, filter=univention.admin.filter.expression('cn', schoolNr.lower()))
+	if not dhcp_service_objects:
+		print 'ERROR: DHCP service object for %r not found' % (schoolNr.lower(),)
 		success = False
+	else:
+		object = dhcp_subnet_module.object(co, lo, position=position, superordinate=dhcp_service_objects[0])
+		object.open()
+		object['subnet'] = str(network.network)
+		object['subnetmask'] = str(network.netmask)
+		object['broadcastaddress'] = str(network.broadcast)
+		exists = create_object(object, ignore_exists=True)
+		if exists:
+			print '%r already existed - usually no problem' % (object.dn,)
 
 	position.setDn("cn=networks,%s" % (getDN(schoolNr), ))
 	object = network_module.object(co, lo, position=position, superordinate=superordinate)