Most likely, your child’s teacher is not making their Posts available to parents. Your child’s teacher has the option of hiding their posts from Parents. If the Teacher has done that, then in order for Parents to view a Note, the Teacher must type in the Parent Group when creating the Note. Otherwise, Parents will not see the Note.
Keep in mind there are some types of Posts you’ll always see, such as Assignments, Quizzes, and Direct Messages between your child and your child's Teachers (learn more about what you’ll see here). But other Posts may not be automatically visible to the Parents depending on the Teacher's settings. Check with your child’s teacher if you have questions about Posts not sent to you, and feel free to direct them to our Help Center page about sendings posts to Parents.