Lots of lazy teenage boys in my family and most eventually turned around. What didn’t work: a rigid hand, threats, adversarial positions. For the boys in my family, that just set up conflict between the parents and son and they often rebelled.
What did work: lots of support, getting the student into more activities, organizational tutors, counseling.
Have you had a talk with the school guidance counselor? Are there any engineering courses in his high school? Have you looked into summer engineering programs? Some areas even have Saturday or afterschool math or engineering clubs. Get him more involved in his interests so he’s more invested. Stay on top of his math grades and offer him some sort of reward for bringing home As in math. Don’t worry about where he might go to college: there are directional state universities with engineering degrees and you can even start an engineering degree at the community college. The important thing is giving him the skills to get through the program and those skills involve math, better time management/ organization and motivation.