I have done this type of correction with a one step procedure on 5 young women between age 16 and 18. So far, all have been happy with the result. They had to be fully grown, have parental consent (in California) and have adequate scalp laxity for the amount of hairline lowering desired. If you are male, this operation or hair transplants should only be done at your age if there are severe psychological concerns. Male pattern hair loss could leave you with a noticeable scar even if it is a fine white line.
High forehead in adolescent male
You have a challenging problem but at your age, your options are limited to use of tissue expanders or hair transplants that may not withstand the test of time as you age. Costs will be considerable so you really have to ask yourself how badly does this impact you before jumping in.