You will need an admin on the server to add your name to the whitelist.
This can be done by changing whitelist.txt or using the command /whitelist add (name)
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You can. The server just has to be on when you try to join or the server is whitelisted and you aren't on the whitelist.
There could be a number of reasons. (A) he/she might be using the browser to try to connect. (B) if it's a public server they might be "whitelisted". (C) not sure bout this one but they may have a mod unsupported by the server. Hope this helps!
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You can email Minecraft if you have any questions about Minecraft. That's what the Minecraft Help Email is.
There are no schools in Minecraft and/or a school that teaches minecraft.