Actually, to be very transapert, what you are thinking, its the approach of maximum students, who went through JEE drop and unfortunately couldn’t qualify.
I would like to suggest you,
1. Right now, you are in B grade private college, there may be less chances of placement, total time- 4 year
2. If you take a drop, may be or may not be you qualify for NITs or DTUs, then again same scenario....
In case you qualify, you would earn B Tech in four year, may you get placement.....you know the risk and confidence.. total time spent(1 + 4) year
The best option you can have....you have to be very comprehensive about the GOAL
…. Carry on your Bachleor degree from same college and prepare parallely for JEE Main, you may join a test series online or offline..........syllabus in first year of Engg is almost same as of JEE Prep.
If you qualify for JEE, then a good chance otherwise continue your degree and third year onwards, start preparing for GATE that would be direected to good PSUs or M.Tech from IITs.....and two year of prepration is enough to get good score in GATE.
total time spent(4 + 2)year = M.Tech …..
So stay focused towards target....Good Luck..
