That's a tough one. Working for those companies has ups and downs (as you know). Many times, they have you sign something that restricts you from working for the district(s) in that are for some number of years. Different companies have different policies as far as how you get retirement and the benefits you can access, etc. They may be considering whatever benefits and/or perks you get as part of the compensation package and feel it's similar to what those in the district get.
When I worked as a counselor in the school district where I had worked as a teacher, I got credit for all of those years because counselors were on the teacher pay scale. Since you worked in a different district as a teacher, it's hard to know what you would be making or what they would give you credit for in the district. However, knowing that your friends were able to get more money clearly says it's possible.
Can you contact HR at the school district and ask about the level of compensation you would get with your experience? That might give you more to bargain with. If you don't have a restriction against applying to school districts, I would consider applying if there are any openings. Other than that, I"m not sure what else you can do.
