Everybody that speaks in the vein of loyalty (ie honor your commitments) forgets these are the exact same districts that will RIF you in a heartbeat or choose to non-renew you your first year and not give notice until the school year ends. The knife cuts both ways. Use the law to your advantage, and if you resign before the 45 day window passes, they can find a suitable replacement.
Think of it this way. I told a colleague one time as we left for spring break "have fun, don't die! Because if you do, we'll have your job filled here within a week". It's a daily reminder that the job will never love you back, you're replaceable, so be your own strongest ally and advocate.