It's as normal as any public school contract can get from what I can see. But do make sure that this public school will pay for the Health Check, Resident Permit, and that they will get the Foreign Experts Certificate for you. If you need to make a trip to Hong Kong to get your Z visa get them to reimburse you for the trip too. They may ask you to pay for all of these first though with the promise of being reimbursed later. Do stay on them about this if this is how they will proceed to obtain legal working status for you.