The singer made an appearance at the Bitterne Park school with Radio 1 DJ Scott Mills, who claims that Will acted like a "k***" by ignoring his supporters.
"Will used to be a nice bloke. I don't know who he's been hanging out with, but now he's just a k***," Mills complained. "He refused to meet any of the children, banned all cameras and had loads of kids in tears."
A radio source told The Mirror: "Everyone at the school was so excited that Will Young was going to be there, especially the children. But when he arrived he wasn't interested. There was really no point him coming at all.
"A lot of the children had been really looking forward to it, but they went home disappointed. Some of them were even crying."
However, a spokesperson for Will has insisted: "This story is ludicrous."