No they didn't, and our school offered government-provided, surplus peanut butter with which they made 5 cent sandwiches. However, that does not mean that the problem wasn't there. They just didn't know what caused the kids to be sick. My cousin died from previously undiagnosed diabetes during that era, and she was under the doctor's care in a hospital at the time! Medical personnel are much more knowledgeable these days.
My little granddaughter spent several days in the hospital last winter because well-meaning friends brought dinner to the family that included brownies that had no visible nuts. Her mother was restricted to bed with a strained back. The brownies were Little Debbie's and had been removed from the wrapper and placed on a pretty dish before they arrived at the home. My son served them to the kids after checking them over carefully, but there were invisible ground nuts in them. Poor little Lydia wound up in the ER, unable to breathe, and spent a couple of days on oxygen. This was a case where the brownie had been baked in a facility that also baked items that included nuts, and they are not always as careful as they should be about cleaning everything between recipes. It's those pesky oils and essences again. They just linger. (And nobody got sued over this incident.)
With all your background in nutrition, I'm sure that you could come up with a suitable substitute protein for your child's lunch. Or, you can continue to keep your child home and continue to blame the "unfair" folks who run the schools who are "distriminating" against your child who is on the self-imposed limited diet. It's your choice, and you have made it. I'm glad you are happy with it, but it may limit your child's experiences in the future.
I can assure you that no one with severe allergies wants the world to change for them. They just want to stay out of the hospital and out of the grave. To use your own words, "This is not a matter of [my] the child's desires. It is a matter of her health"