How strong a lock you need depends on many factors.
- Is this a bike that appears to be worth $50, or does it appear to be worth $1,000?
- Will you be locked up in busy public locations for an hour or two during the day, or locked up 24 hours per day?
- Will you be able to lock up next to a large number of bikes that are clearly more valuable than yours?
- Does your college have first rate bike racks that are watched closely by the campus police?
At the largest campus in my neighborhood, most students ride "junk" bikes that are old and rusty. If a student has a "new" bike, it is a $75 Wal-Mart bike or a $300 bike from a discount bike store. I NEVER see a nice new Trek or Cannondale parked on campus. Such a clearly valuable bike would be WAAAY too attractive to crooks. No lock could protect it for long.
So, if your bike is worth more than $500 or so, I'd suggest going to a resale shop and buying a $50 bike for on-campus riding. Less attractive to crooks, and you wouldn't miss it much if it gets stolen.