Officers attended Hopwood Lane at around 12.23pm and found two males, aged 15 and 16, wounded.
They were taken to hospital with serious injuries which are not believed to be life threatening.
Three males have been arrested and have been released pending further enquiries.
Detective Sergeant Nick Speed, of Calderdale District CID, said: "This was a serious assault where two people sustained serious injuries, but the consequences could have been much worse.
"Officers are continuing to carry out enquiries but I would appeal for anyone with information to get in touch with police.
“This incident happened on a busy road, with lots of people in the area at the time. I would ask for anyone who witnessed this incident to contact officers.”
Anyone with any information is asked to contact Calderdale CID via 101 quoting 13170411518. Information can also be passed to Crimestoppers anonymously on 0800 555 111.