This movie gives activities to help with explaining these choices 

Below is a link to lists of words to help you with the activties in the movie.

Word Lists - long vowels

The link below takes you to an A4 sheet linking the most common long vowel spelling choices with the position of the long vowel sound. You can view this online or print it  as a memory aid for the learner, ask in school if you want a printed copy but have no access to a printer.

Long Vowel Choices Desk Mat