如果见面，礼貌地问她，我的孩子有什么需要improve 的。这样能引出她的观点，又不显得defensive. 信的称呼务必加De

Dear Mrs. X,

I am the mother of A, who is in class xxx and currenlty taking science class with you. Is it possible for me to meet with you to discuss A's performance sometime next week ? I will be at YYY School on Monday to attend the Awards Assembly and will be available anytime next week except Tuesday morning. I  look forward to hearing from you.

Thank you.

Best regards,

B (A's mom)

见面用语：（诚挚地） Is there anything I can do to help him improve? 看这老师怎么回答。英语口语中这种问法是绵里藏针，既客气又咄咄逼人的。