I understand there's a rule for checking in bags, but how strictly is this enforced for a standard size backpack? Do they only allow very small bags/purses or do they force everyone to check them? Just would like some recent feedback. Thanks!
The smaller you make the bag look, holding under your arm as opposed to slung across your back, the better the odds. It really just depends on the security guy you go past and what they ask you to do. They are looking from a security and possible damage perspective so smaller is better. Most standard daypacks would not be a problem, but a true hikers backpack probably would be.
That depends on what you define as a standard size. A small backpack, probably no bigger than a woman's purse (think man-purse) would probably be OK. Something along the lines of a camera bag or messenger bag should be OK as well.
The backpack I'm thinking of taking along with me is one I use for school and is about 18"X24" in size. Is that too big?
Your 18x24 should be o.k. That's about the size I used and we got in fine with no problems.
Taking a school backpack inside the museum is ok.