ChatGPT is blocked for students for sure, and will continue to be so for the foreseeable future. Right now, students can access Educational AI such as School AI (as you mentioned), but also an AI chatbot through Securly called Securly Chat, which will be the only GPT like chatbot open to students. To access, students simply go to chat.securly.com.
In terms of support for School AI, since your school has a premium subscription trial for the rest of the year, School AI offers tons of training modules on their website. Check out this resource that Rena gave out at the School AI training a few weeks ago, it will tell you how to access those course modules.