The incident took place around 2:40 p.m., Wednesday, Jan. 8, near Uniondale High School at the corner of Walnut Street and Leslie Lane in Uniondale, said Nassau County Police.
According to detectives, after leaving school, the boy was confronted by a group of unknown males and was attacked with items, including a baseball bat.
The teen suffered a non-life threatening stab wound as well as a head injury that was caused by being struck with the baseball bat.
He was transported to an area hospital and is listed in serious but stable condition, police said.
Detectives request anyone with information to call Crime Stoppers at 1-800-244-TIPS.
All callers will remain anonymous.
Click here to follow Daily Voice Suffolk and receive free news updates.