In the fourth and final quarterfinal, Shanu Majumder scored twice (4th and 47th minute) while Prakash Sarkar chipped in with a goal in the 32nd minute. For Assam, Pranjal Moran struck the solitary goal in the 10th minute.
Kalyanghar will meet Government High School, Meghalaya in the semifinal.
Greenwood School, Nagaland have already booked their berth in the final of the tournament.
In the girls' under-17 section, Our Lady of Rosary School, Goa booked their quarterfinal berth as the second best team from Group I when they thrashed Air Force Bal Bharti School, New Delhi 4-0.
The Goan needed to win their last league encounter for safe passage to the last eight and they did that in style, thanks to a hat-trick by Keenda D'souza who found the net in the 3rd, 16th and 32nd minute.
In the other Group I game, Offee Lalmingahualpuia scored her third hat-trick in as many matches to help table toppers Government Mizo High School, Mizoram thrash Baroda High School, Gujarat 5-0 in an one-sided affair.
Later in the day, Sri Ramakrishna Saratha Higher Secondary School, Tamil Nadu blanked Air Force School, Subroto Park, New Delhi 5-0 to start their campaign on a winning note in Group II.