Would ya look at this little Brit! Isn't she so darling in this yearbook photo, posing in one of her finest sweaters and a cute flowery blouse?

Nowadays, this pop starlet can be seen wearing a lot more makeup and a lot less clothing -- her signature look as of late seems to be thigh-high tights with combat boots and oversized jerseys, a far cry from her days as an angelic school girl. As one fourth of one of the U.K.'s sexiest and sassiest girl groups, however, the 20-something singer's hot new look suits her... and then some!

Have you figured out who this pop star is? Click through to find out!