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My first thought is that you're attempting to connect to a different network than everyone else.
This type of login screen is an authenticated user. If it's just a password protected Wifi, there wouldn't be a username field.
Does he have a network login that he uses when logging into school computers? It would be like johhny@highschool.com Depending on the setup, you might leave off a portion of that.

If I was the school admin, I'd test the login on a school owned computer to ensure the login itself works.
 
Yes, he is assigned an email account and pw there has been an issue with his email account i think that maybe one issue. I think the issue was how his last name spelled out my last name plus my husband's. I'll have to see about that they may need to reissue one.
 
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