I would ALWAYS choose spring break over summer, because I can manage large crowds much better than I can cope with the heat and humidity. I've been to WDW over Easter week (the week AFTER Easter) numerous times over the years. The key to managing the crowds is to arrive as early as possible to get on as many popular attractions as you can before the larger crowds arrive. Then use Fastpasses while hitting some of the less popular things in between.
If staying on property, it also works great to take a break for the afternoon to swim, nap, shop, or whatever. Then if you return for the evening (parks are open very late for Easter week), the crowds get lighter, especially after fireworks, etc. are over.
For you, it may boil down to deciding which is the "lesser of two evils" - the heat or the crowds. For me, I pick crowds over heat any time, while others would choose the heat.
Do you have any other winter break or school vacation when you might consider a visit? I LOVED going in Jan. and Feb. of this year. The weather wasn't always great (cold for us in Jan. and cloudy/drizzly for us in Feb.), but the small crowds were absolutely wonderful. Such a nice relaxing way to do the parks!
Congratulations on becoming a teacher! We need more good teachers in this world. I wish you well in your new job!
