Looking for the reason for a ban

[riskybubbles]

Hello,
My 7 year old son played on your server for the first time yesterday (ufo8). Today he tried to log in and it said he was banned for using a modified server? I don't understand what that is. He has minecraft 1.15.2. If we're doing something wrong please let me know so I can fix it. He really enjoyed playing on your server and hopes to be able to play again.
Thank you.

[Thoatt]

I was the staff that banned ufo8. They were banned for flying in an area that does not have fly, which means they would have to be using a modified client to do so.