ACT public school teachers have taken industrial action for the third time this year, with schools opening two hours later on Thursday.
The action is due to protracted negotiations on a new enterprise agreement, with the possibility of future full-day strikes flagged.
The ACT government says pay negotiations are progressing and the focus is turning to workloads.
Primary school students Thea and Elvy Bundey said they have spent much of their week colouring in instead of learning.
Due to staff shortages, their classes have been combined, resulting in 63 students being in one class.
Schools across the ACT were closed for two hours on Thursday morning as Australian Education Union members stopped work to letterbox communities about the situation.
Freya Bundey, who is also a teacher at Dickson College, said the public school system was in "crisis".
The union's ACT branch president Angela Burroughs said the public education system was "suffering from chronic understaffing".
Education Minister Rachel Stephen-Smith said negotiations had made some progress, on pay, but said there was still work to be done.
Some schools are facing a drop in their funding, but Ms Stephen-Smith said only indicative budgets have been released so far, with final allocations still to come.
Ms Stephen-Smith said an "exceptions bucket" of money would be made available to schools that tried to meet the conditions of the new funding model.