Do you mean Feb 2012 so 50 seconds in 4 months is a tough call for anyone. So physical training depends on where you start and your mental training (willpower, stamina, suffer-capacity) depends on where you want to go and HOW MUCH you want that goal.
Facts: (current status):
Run as far as you can at 4:20 pace(70.4 s/lap); so how far did you get?
You are currently running 82.6 s/lap for 5:10.

Look at how much you are training now and what your principal focus is?
Is it 1500mtrs?

How strong are you, try Frank Horwill's hop test?

Are you racing now or have you stopped for the "fall/winter"?

Future:
Make sure you are strong with hills, steps, specific weight training and guided plyometrics.

Maintain a good volume on cross country or roads for the next 2 months and maintain at 1 or 2 track sessions. Keep everything going at a good pace and dont run too slow too often.
In December/January
Dedicate at least 3 days per week to goal pace training intervals with increasing pace or 1 session, goal pace for another and longer intervals for the third.

Dont forget your recovery strategy to maintain health and fitness through good eating, adequate water intake and recovery including sleep and rest.

All this makes no assumptions about everything else in your life such as school. work, family, access to facilities etc.

Have a good fall/winter and get that goal !
Dai Roberts, Senior Coach, Dai Roberts Group Inc. Virginia Beach, VA.