OP - it has to be a Mass HE cert, per chapter 269 of the MGLs. This is because some of the basics of Mass gun laws are discussed.
Just so you know, there are some towns that will not honor the HE Cert for FID/LTC issuance. In that case, you have to either suck it up, and take an LTC course (Don't take one that's only good for FID issuance, e.g., Basic Shotgun), so you don't have to take an LTC-suitable course, again, or try to fight the Machine.
Oh, some towns "Forget" that you have a discounted rate, so print out the section of Ch. 140 of the MGLs in case they don't know. You also need a letter of parental/guardian consent, as you're <18.
If you don't have a mentor, join a Club, and find someone that can show you the ropes.
Welcome.