The two teens claimed they were beaten up by nine people for no reason.
Chinese national Fan Xing, 17, was left with a torn lip, dislocated jaw and swellings on the head, while Taiwanese national Yang Jet Jin, 19, had a broken nose and bruises to his eyes.
The teens, who called The New Paper hotline, claimed they were not part a gang.
When probed, Fan Xing said he had quit Secondary 4 at Balestier Hill Secondary School this year because of conduct problems. He declined to elaborate.
Their ordeal, they claim, began on March 15 when Fan Xing and Mr Yang, who is a Secondary 5 student at the same school, were at a coffee shop opposite Shaw Plaza in Balestier.
They were having dinner at about 5pm when they received a call from friends.
Said Fan Xing: "(He) told me to head down to 'slack around' at the void deck of a HDB block like we usually do, so I did not sense anything fishy about it."
When they arrived at Block 102, Jalan Rajah at close to 8pm, a group of about nine people were sitting around a table tennis table waiting for them.
The boys know several people in the group including two whom Fan Xing called "close friends".
No one said a word and one of the group suddenly charged at Mr Yang and threw a punch at him.