Long menu - fatal error, out of memory

I'm working on an education tool for a Bay Area school district using Drupal. I decided to house all the lesson plans under the site as well. Everything was going smooth until I went back and started creating menu items for each lesson as there are quite a few. Well, there are 10 subjects. 8 grades. 8 lessons per grade. I knew the menu was going to get pretty long. But I didn't necessarily anticipate a limit to the number of items I could have in a menu. I've been able to fix other out of memory errors by increasing the memory. Needless to say, somewhere towards the end, I've been unable to get to the menu via Adminster to turn on or disable menu items because of memory errors. The other menus are fine. But when I click on the lessons menu, i get that dreaded white screen shouting out memory errors. I've increased the php memory to 500MB and STILL get these errors. Yes, I have too many damn lessons I'm trying to shove in the menu causing it to be quite long. But... is there anything I can do to fix the memory issue with the menu that I'm overlooking? I feel like my only other option is to now go through every lesson i just painfully entered and remove the menu item until I can get in. Help?

I get:
Fatal error: Out of memory (allocated 43253760) (tried to allocate 2921715 bytes) in /..../htdocs/includes/form.inc on line 2036
first.. followed by an error in the menu include if i try to go there again.