sir/mam i m in cls 12th right now next year in 2020 there is my board exam after that i want to prepare for jee and advance and sir/mam i m a average student not extraordinary student which institute is best for me if i will do hard work for my target

Hello,
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If you really score good and try your best. Here is the list of top colleges for jee students which can help in achieving a great career.
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• Indian institute of technology, Madras
• DR br Ambedkar national institute, Jalandhar
• Graphic era University, Dehradun
• Indian institute of engineering science, shibpur
• III technology, Ahmadabad
• Indian institute of technology, Indore
• Indian institute of technology, Mandi
• Jamia Millia Islamia, new Delhi

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and many many college you have in a list to Choose. firstly choose a state and then go for college selection.
Here is the link in which you Check many other colleges and there brief details.
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https://engineering.careers360.com/colleges/ranking/top-engineering-colleges-in-India-accepting-jee-main-score