must and mustn't

For homework:

http://www.englishexercises.org/makeagame/viewgame.asp?id=2786
http://www.englishexercises.org/makeagame/viewgame.asp?id=5140
http://www.englisch-hilfen.de/en/exercises/modals/must_not.htm

In the classroom:
SHOULD: http://www.englishexercises.org/makeagame/viewgame.asp?id=1734
https://elt.oup.com/student/project3rdedition/level3/unit6/grammar/exercise1?cc=global&selLanguage=en

http://www.englishexercises.org/makeagame/viewgame.asp?id=8128
ALLOWED: http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-63918.php

Saint george's day

http://www.esolcourses.com/content/topics4april/stgeorgesday/pre-intermediate/warm-up.html
http://www.esolcourses.com/content/topics4april/stgeorgesday/wordsearch.html
http://www.esolcourses.com/content/topics4april/stgeorgesday/picture-vocabulary.html

spot the difference

https://f6c7z5k9.map2.ssl.hwcdn.net/wuploads/preview_new/full_57414_spot_the_differenceat_the_beach_1.jpg

https://sevenastious.files.wordpress.com/2013/10/find-the-difference-present-continuous.pdf