College application for composition

Hey, I am fairly new to composers community and what to take it seriously. So planning on applying to college after my graduation in engineering. 

My question is I do not know what does a good prescreening portfolio consists of. I mean what all should be done to have this portfolio to be impressive. Also they ask for original scores. Any tips on what style and depth they look for in these original work as I don't think the accept pop music composition... 

Does it have to be strictly classical? 

Any help would be very appreciated.Thankyou.

Perhaps you should write to the college that interests you, and ask them for guidelines of what to submit..  Many many years ago (1970), I applied to a traditional music college.  I played a very short Bach piece, and repeated it, playing my 'beefed up interpretion'.  The teacher started screaming at me, 'how dare I try to improve on Bach'.  I was reduced to tears.. 

Man it was ugly. After I calmed down, we had a great talk, he asked me about my passions, rock music, and he took me to their new 'electronic music department'.  I saw my first synthesizer, an ARP2600.  It was like fireworks for me. I instantly fell in love with this new strange instrument. And that has been the passion of my life ever since.

Good luck in your endeavors.  The world needs more musicians and composers.  It is good for you, and good for the planet.