According to Gray's anatomy, cartilage is avascular but in a recent class, my teacher told me that there is vascular supply but it is confined to upper surface only. So, I'm confused that who is correct.
This depends on what kind of cartilage you are examining and where it is located. Cartilage is not all the same depending on where it is located and it's intended purpose. Cartilage also generally exists as a continuum with the bone that it is attached to where you will see transitional changes from bone tissue to cartilage without specific delineation. Depending on the cartilage location and its function it may of may not be vascular. Hyaline cartilage existing closest to synovial joint spaces is pretty much entirely avascular. This has some advantages and disadvantages. Damage to cartilage is very difficult for you body to repair for myriad reasons one being avascularity, but also the avascularity allows for you to transplant live cartilage to any person regardless of what tissue type the donor or recipient is.