I am a teacher of elementary school students ages 7-9 years old. I am not a chess player with much experience, however I recognize the many benefits of children learning and playing chess. Within my classroom we play chess as part of our weekly plan. To give greater independence in deciding if a checkmate is valid, I created a poster with a three question test for students to use:
How To Test A Checkmate:
Can the defending king move out of check?
Can a defending piece block the check?
Can a defending piece take the checking piece?
If the answer is ‘no’ to all three questions: the checkmate is valid.
This has been very useful for my students. Is there any way to improve this test? Are there any errors or omissions? Are there any unusual checkmates where these questions would not apply? Your suggestions will be valued.
your test is valid and useful.
You don't need to use the term "defending".
Just say: If "any piece" can block the checking piece. and If "any piece" can capture the checking piece.
There could be a piece (for example: a bishop) at the far end of the board, far away from the king, and is still able to block the check.
This bishop may not be a defending piece in the strict sense but could be more of an attacking piece which attacks the enemy kingside at the same time, but is still able to defend a check by retreating and blocking.