hi,

see in 12th course you may get options to select subjects among biology, statistics, computer science etc. since you are interested for ethical hacking you should choose computer science as 4th subject taking physics, chemistry and mathematics as a mandatory subject. however the syllabus may not have ethical hacking , it would depends on the board of education and their prescribed syllabus , however you may learn by yourself by watching the you tube video or taking course in udemy, coursera like platforms.