This is a very simple sheet to use for beginner ear training. I play 2 notes one after the other and the student circles the correct symbol. I kept this worksheet straight forward so that I could adapt it to each student easily. It is also free of childish illustrations so can really be used with any age, and although I use it to teach piano ear training, I imagine it would work just as well with other instruments.
How to make it easier:
1.Make the intervals bigger
3.Talk through what you are playing "Now here's the second note" etc.
4.Let them watch! Not exactly ear training but still perfectly valid for young kids
How to make it more difficult:
1.Only use small intervals
2.Play quickly or use staccato notes
3.Don't speak at all until the worksheet is complete
4.Play very high or very low notes, these are generally more difficult for people to hear clearly