Does your DC attend a school which releases information on what school trips will be potentially offered throughout the school journey and rough costs rather than communicating trips in isolation with no information as to what if any other trips may be available during their time at school?
At DD’s school there were no trip offerings in years 7-9 then three in year 10. Not getting selected for one didn’t give you a better chance at the next trip so some students were selected and went to more than one (2 trips around 2.5k and one <1k.) No information at that time on whether there would be any future trips (will be asking them).