Hiiii Nilesh!!!! To appear in engineering entrance JEE mains, the conducting authority, NTA, has released compulsory subjects to appear in the exam. According to it, it is mandatory to have 5 subjects in 12th. For B.Tech and B.E, the subjects are

• language,
• physics,
• mathematics, 
• Chemistry, biology, biotechnology, technical vocational subjects ( any one).
• Any other subject

your school will  allow you to change your stream now as you are in 11th then you should change it. Talk to your school authorities. Good luck!!

Hey, 

You can change your stream after completion of 12th from commerce to engineering. 

For B.Tech, Mathematics, Physics, Chemistry are mandatory. 

If you wanna do engineering after 12th, you cannot directly do it but you can pursue a diploma in engineering which is usually 3 years.

Thank you and keep asking. 

Hii,you can switch your stream to pcm(physics chemistry maths) at class11.But remember if u are taking pcm u should study it atleast 5 hour a day.Pcm is tough more than commerce stream they need time for study.Well,you can switch your stream pcm.After getting pcm daily study and start preparing for jee.Jee is an engineering entrance exam.You can give your jee main entrance exam at the running of class12.After clearing it with good marks u can get Iit,Nit or any government aided institute.Then u can enroll B.Tech course which is duration 4 year to make u engineer.Good Luck.