This is my head canon about X-men: first class. Nothing of this ever happened in the real canon, or well, I don't think it did. It'll be mostly Erik/Charles, so if you don't like slash I suggest you just walk away from this tumblr.
The actual reason why Erik put on the helmet wasn’t because he was afraid Charles could read his mind. It was because he was afraid his own thoughts would be too loud for Charles not to hear them shouting.