I'm a parent who is teaching my child how to play the violin. Unfortunately, my child is not consistent about the placement of his left-hand fingers on the fingerboard. For example, when my child presses his 3rd finger down on the A string to play the D note, it is sometimes too sharp, and other times it is too flat.
Are there any exercises that I can use to help him to get the right intonation? Our violin teacher had uses stickers on the fingerboard, but recommended that we remove them since he was getting older. If I recall correctly, the teacher recommends not worrying about intonation for the time being, but letting the problem fix itself when he grows older and his ear becomes more discerning.
Response to question in comment
Question: Is he so far off it sounds like a different note, or just enough to bother a good ear? If he stops to think, can he tell you whether he was sharp or flat, or is he completely unaware?
Answer: That's a great question.
For the first question, the maximum error is about half note off, i.e. if he is trying to play D, he may play D♯ or D♭. But sometimes, he is able to play D perfectly for the entire song of "Twinkle Twinkle Little Star".
For the second question, I have never asked him if he was sharp or flat. Now that you mention it, I should definitely ask him whether he is able to discern whether he is sharp or flat. If he is not able to tell, then I should work on interval training.