In our county (and at least two surrouding ones) it is customary for 8th graders to take a field trip to Washington DC.
Most schools have fundraisers (dinners, magazine sales, candy sales, food sales, and so on) to assist students with the funds needed for the trip which tends to cost several (4-5) hundred per student.
It was not mandatory in any school, only those students that could afford it (or aggressively did fund-raising to pay for their portion) went (now I am not sure how it worked at every school, but I do know it worked this way at four local schools).
Then... you have my DS school (he was there k-9th). It is a very affluent school (we are not) that is in an area where the majority of doctors, lawyers, ect.. live. They chose to have the 8th grade Washington DC trip as well but no... not during the school year as all the other schools did... they had theirs during the summer and at a cost of (get this...) well over a thousand dollars (I thought $1200.00, DS thought $1400.00). There was also NO fundraising opportunities... it was to be paid out of pocket and there were no scholarship type of opportunities!
DS did NOT go of course! I had nephews and friends children (all from other school systems) that went and it was a wonderful learning opportunity! I would have loved for DS to have went, if it would have been awesome and you know what... we could have sacrificed a few hundred dollars as others schools did, or assisted with worthwhile fundraisers (such as selling dinners, maybe even candy bars... you know the nice ones with the fast food BOGOF coupons attached). DS school decided to make it be elaborate and catered to the wealthy once agan.
Now... DS did (growing up) have field trips that all students could go on (but had to pay for themselves) and he missed one other that we refused to pay for. His zoo field trips, COSI, museum, type trips always cost less than $10.00 and usually a lunch was to be packed. The one Cedar Point Amusement Park trip would have cost for the admission ticket, plus spending money, and no packed lunch was to be sent, so easily $75.00 and up. He did not go and had to stay back and go to class all day while the rest of the school was there. He was one of a very few 8th graders that did not go.
The school I recently resigned as a TA from (to attend college

) was totally different than DS's school!
First, field trips were only allowed if planned, proposed, approved and if they were educational in nature (they have to link to a unit or study), with the exception of one school-wide trip to the skating rink. Secondly, there is a parents group that holds various fundraisers years round (nut sales, candle sales, candy bars, ect...) and all money goes into a fund to help the students that cannot afford "things" (field trips, specific school supplies, and so on) or brings fun speakers/programs in. No children were ever left out for the inability to pay, which was awesome!
I do think that schools (administration) need to look at the economy and the daily struggles many families have, before planning/approving field trips. I also think that it should be "all or none"... no kids should be left out because the money is simply not there. Just my opinion!