Dumped sofas, a wheelbarrow and scissors were also shown in the pictures which were sent to councillors on Twitter by those embroiled in the dispute.
The pictures were tagged ‘Bongs, broken bottles, burnt bins. Glasgow Jannies clear playgrounds & keep kids safe’ along with the hashtag #Justice4Jannies.
Janitors at Glasgow primary schools want extra Working Context and Demands (WCD) payments ranging from £500 and £1000 a year.
Some council workers are paid extra for duties which involve physical labour, working outdoors or dealing with unpleasant conditions.
Currently, caretaking subcontractors Cordia do not give additional cash.
Brian Smith, secretary of trade union Unison Glasgow City branch, emailed councillors: “It is just not credible in our view that the working context of a school janitor is the same as a senior council officer working in the city chambers in an office all day.
“That is what the current position of the Cordia board in effect means.
“Thousands of workers in the council and its ALEOs (arm’s-length external organisations) who undertake dirty, heavy, smelly tasks and also work regularly outside receive a Working Context and Demands payment.
“Why are Cordia treating school janitors so unfairly?”
Mr Smith also said 98% of Unison members who were balloted for industrial action voted in favour and the required notification was given to the employer
Cordia said: “A small number of janitors have been involved in this action, but the job they do has not changed since it was first evaluated eight years ago.”
The council said: “This is a matter for Cordia.”