Dalton was Blaine’s home, his safe haven. He could wear his uniform and mask, he could be popular, he didn’t have to worry about being bullied for being gay or being pushed into lockers. The Warblers were like his family except they worshipped him. They would always want him.

Blaine gave up Dalton in Season 3 to be closer to Kurt. He had heard all of the bad things about McKinley from Kurt. He watched Kurt get harassed and tried to help. He heard about the dumpster tosses and slushies to the face. He knew McKinley wasn’t as safe as Dalton.

Blaine knew he wouldn’t be worshipped and wanted like he was at Dalton. Blaine knew the Glee club wasn’t as popular as it was at Dalton. Blaine knew the risks of transferring to McKinley. His parents didn’t want him to at first but he convinced them despite knowing.

He convinced them because he didn’t need Dalton to be his home, his safe haven. He didn’t need to be wanted and worshipped by the Warblers. He didn’t need to be popular because Kurt was his home now, Kurt was his safe haven.