I�ve used WordPress.com to create free blogs and I�d recommend it. It works well, is very widely used (so has support if you need help) and looks professional. They want to sell you themes and plans, but you can still achieve great results for free.
I�ve also used WordPress.org to create websites on my own domains. You have more choice and freedom, but it�s a steeper learning curve and more work.
This page explains the difference between the two: https://en.support.wordpress.com/com-vs-org/
That webpage that Alex linked to above, for example, was made using WordPress and a �
theme� that the author applied.
Some links:Google search: https://www.google.com/search?q=create free school online magazine
Step by Step Guide for WordPress Beginners http://www.wpbeginner.com/guides/
WordPress download https://wordpress.org/download/
18 Magazine WordPress Themes: https://theme.wordpress.com/themes/features/magazine/?sort=free
9 Tools to Create E-magazines and Newspapers for Your Class ~ Educational Technology and Mobile Learning http://www.educatorstechnology.com/2012/11/9-tools-to-create-e-magazines-and.html
Create your mag for free: Madmagz https://madmagz.com/
WordPress.com: Create a free website or blog https://wordpress.com/
How to Start a Blog (Free Beginner �s Guide) - The Blog Starter http://www.theblogstarter.com/
The 10 Best Free Blog Sites | StyleCaster http://stylecaster.com/best-free-blog-sites/