Could the school host a race pigeon event, each pigeon being allocated to a child.
ballon releases are stupid, especially as the children have the most to lose when the environment is damaged,
Helium is a finite resource,
SAT divers breath a combination of oxygen and helium , it costs about £10 a breath, and makes them talk like a cartoon character, (hard to understand on the phone)
With at least three to six divers in each SAT, and three or four SAT on each ship going 24 hours ,7 days a week, 52 weeks a year, it's a lot of helium, and there are a lot of ships.
because of the rising cost of helium what they breath out is now recycled,
but it's the elephant in the room, because without SAT divers there will be no oil, without helium, there will be no SAT divers,
the helium will run out long before the oil,
so when everyone thinks, oh well oil is running out, but in my life time it won't really effect me,
it's not the oil we need to worry about.
Helium is also vital in various medical procedures ,
so filling ballons with it is very short sighted and stupid, and that's before you even think about the litter problem.