Check with your school administration and find out how the grades are posted - if online OR printed and delivered to students! If HISD go to their website and it should let you ask questions and follow the prompts.
You can go to my website and check out school finders for more information!
Most schools now have a specific website and an assigned ID and PW for each student. Like my associate suggested, it better to contact your child's school directly or send a simple note to your child's teacher with this question.