Your child's teachers (and afterschool providers) are a good source of information about your child. Plan to interact with these individuals early in the school year and routinely thereafter. Information gathered through these conversations will support you in doing math with your child at home.
You might ask:
What math will you teach this year and how will you teach it?
What are your math goals for my child? for the class as a whole?
How can I best support my child in math in ways that are in-line with what is happening in class and/or the afterschool setting.
My child is saying ...about math to me at home. How can I...?
What are the best ways for me to communicate with you?
You can also ask the teacher to share examples of student work with you. For instance, if your child is struggling with addition and subtraction, ask the teacher to explain how other students in the class are solving these problems and to show you some samples. S/he might also share some ideas about what you can do at home to help your child understand, use, and practice one or several of those math strategies.
Teachers report that it is important for families to inform them if their child does not understand an assignment or has difficulty with a particular concept. If you are unable to talk to your child's teacher in person, write a note with your questions so that the teacher can address these issues in class and help you work with your child at home.
If you are looking for additional information, some schools and districts have math staff developers, coaches and teacher-leaders who may be helpful to you.