My husband’s grandparents went through something similar. His grandfather was older and a bus driver for the school district. At the time the condition was bus drivers could not be married at all. His grandmother was a senior in High School but aged 18. They got married in September and hid it until graduation in May. We still have the graduation/marriage announcement where they stated they were married the previous fall.
I did not change to my married name until I received my degree. I feel so bad still, I love my husband and proud to take his name. He supported me through getting my degree and had no problem with it.... Love him so very much. Amazing man!