A chest X ray is about 0.1 mSv.
https://www.energy.gov/sites/prod/files/2018/01/f46/doe-ioni...
On the one hand, it's a lot of radiation, but on the other hand, that's a very long time to live. Sounds like a pretty good deal to me.
A very slightly worse school will likely have a much bigger effect on your kids life expectancy.