Other passengers in the bus should ask them to stop doing all those rubbish things. if they still not stop, the bus driver should take strict actions on those students by contacting their school teachers and telling them about what they are doing.
campaigns should be started to spread awareness to make people more sensitive towards senior citizen. In schools teacher should teach the students not to trouble the elderly citizens.
i hope this helps you, if you like it please mark as the brainiest and also like :)