Academics

As stated previously some of the classes can be pretty difficult, however they are also beneficial.

It depends on the program. I started out pre-pharmacy and had a lot of trouble keeping up, especially with chemistry.
My suggestion with these courses is you need to know the basis for the science classes. So, if you know you're going to be taking one (gen bio+, gen chem+, anat and phys, math, etc.) then go ahead and start earlier with your tutor and get help understanding the basics so that mid-semester you're not having to do double the work.

will challenge you in the classroom

From what I've heard the sciences can be pretty hard, as well as classes in specific majors, but general classes aren't too challenging.

Depends on the teacher.

The classes are not that difficult if you just take time out of your schedule everyday to study. An hour or so everyday helps more than you will even imagine.