Here are two of the key documents in the dispute between parents of football players at Loudoun Valley High School in Purcellville, Va., and the administrators of the school and the district. The first is a general proposal, jointly prepared in February by Brain Sentry and Inova Neuroscience Research, to outfit all of Loudoun’s football and lacrosse players, at a cost of $50 per sensor, and then study the data from the sensors. The second is a letter sent to the football parents on Wednesday night by Loudoun Valley’s top administrators, making clear that the sensors shall not be used.

First, the Brain Sentry-Inova proposal, from February:

Now, the formal response from Loudoun Valley High School, sent Wednesday night: