Dear Student ,

As you want to become an UI/UX designer or Frontend web developer , so .. it would be better if you pursue BCA or B.Tech in CSE or IT .

Look , in BCA course ,there are several topics on Programming , DBMS, Operating systems etc.

To become a good web developer , a good /basic knowledge of programming is required . Mainly in Frontend web development , you need to know HTML, CSS, JS, React . As you are in now 12th grade so you can do some online courses also on web development in some popular platforms like Udemy, Coursera ,Swayam etc.

For more details about Web Development , you may refer this:

https://www.careers360.com/careers/web-developer

Hope this helps !