To study fashion designing after 12th grade, you can consider diploma courses, degree courses certificate courses admission to all these courses is based on entrance test. after choosing the course you need to find right college NIFT is one of the finest university for this course or look at the multiple options provided in link

https://www.careers360.com/courses/fashion-design-course

You can also gain hands-on experience through internships, stay updated on industry trends, and build a portfolio. Networking is also important