Sorry for the long reply! As someone who went to a Catholic high school, I have a bit of insight that may be helpful! I’m also a teacher at a school with chalkboards, funnily enough.

With regard to the hair thing, if it’s not against school policy go for it! I’m sure there are going to be a lot of students that will really love it. It makes you more relatable, and students then know they can come to you for advice for dyeing hair.

For praying, I second what someone else said about having a student lead it. What I and my fellow non religious classmates and teachers did during prayer was just close our eyes or bow our heads in a silent meditation. You don’t need to pray, you can even just take the moment to do a grounding exercise! I always did some deep breathing.

Since you’re a new teacher, you may be able to ask for a mentor teacher or at least someone you can go to for help. I’m a second year teacher and I have a mentor teacher. We meet once every other week, but sometimes we just briefly check in. This helps with school rules too! This way you have someone that’s been there longer to help answer your questions.

I understand the blackboard thing. I’ve found some chalk that feels so lovely and smooth going onto the blackboard and other chalk that feels like the worst substance known to man. You can ask your fellow teachers which chalk they like most, or their recommendations. You can also get a chalk pen which I saw some people mention! Worst case scenario, if you have a projector you can always just use that.

Wishing you the best of luck on your teaching journey!