Adil Rashid, 18, claimed he was not aware that it was illegal for him to have sex with the girl because his education left him ignorant of British law, Daily Mail reported.
Judge Michael Stokes handed Rashid a suspended sentence, saying: "Although chronologically 18, it is quite clear from the reports that you are very naive and immature when it comes to sexual matters."
Earlier, the Nottingham Crown Court heard that such crimes usually result in a four to seven-year prison sentence.
The judge, however, said since Rashid was "passive" and "lacking assertiveness", sending him to jail might cause him "more damage than good".
Rashid, from Birmingham city, admitted he had sex with the girl, saying he had been "tempted by her" after meeting her online.