Hi, If your child is attending school in the United States, the best way to get your question answered is to contact the school or school district directly. Enrollment deadlines vary.
If you don't already have the contact information for your child's school or school district, Education.com has a free resource you may find helpful. It's called SchoolFinder and you can access it here: http://www.education.com/schoolfinder/
Simply type in your city, state and/or zip code to review a listing of schools in your area. Click on the school and/or district page to get its contact information.
I'm also including a link below to some information about preparing your child for Back to School. I hope you find these resources helpful to your family.