Parents could be given a choice and no one who wanted to go is excluded from the school activity due to low income.
Of course there will always be other reasons for pupils not taking part in activities, but it is just illogical reasoning to say because of this it's OK to exclude poorer children from some activities.
Not everyone has to be in the school play but everyone has the same opportunity to be regardless of income.
Not everyone has to be in the chess club but everyone has the same opportunity to regardless of income.
Some children may not be coordinated enough to gain much from trampolining after school club but they are not exclude due to income.
Excluding on the basis of income are the objections on this thread, not going on trips for a variety of ther reasons does not in any logical way negate that argument. Even if you disagree with it, this is just very silly extrapolation as Portofino said.
You don't have to go on a trip: your parents may not want you to, you may not want to, you may be off school that day, a specific trip may cause you difficulties for personal reasons, these may be valid/not valid, we could debate each one separately, but still: you shouldn't be excluded because your parents can't afford it. Or not. That's the argument on this thread.
Some very odd arguments being put forward here.