The state government has rejected the latest wages offer from the Australian Education Union in favour of the dispute being handled by the Tasmanian Industrial Commission.
The union said their offer which "fixes" the state's latest agreement was delivered to government last week.
AEU state president Helen Richardson said the government's referral to the TIC only covered wages and would not deliver improvements to conditions.
"It can't deliver anything on workload and recruiting new teachers and it won't help beginning teachers or principals who need extra support," Ms Richardson said.
"The government's latest offer included the recruitment of 169 specialist teachers in maths, music, language, art and STEM to deliver workload reductions in 2020 - it's something we both agree on but it can't be delivered unless we reach agreement soon.
"Arbitration at the TIC would take far longer, cost much more money and wouldn't even consider the highest priority for teachers which is workload and student needs.
"The union and government have already agreed on the bulk of an agreement, we could settle this before school returns next week if they would just sit down and negotiate in good faith."
Government Minister Guy Barnett said the government's position was very clear in referring the matter to the TIC.
"We made an offer to teachers ... the teachers themselves wanted to support that offer and then [the union] did a total backflip," Mr Barnett said.
"The position of the union is very disappointing."
Labor education spokesman Josh Willie said the government had missed an opportunity to resolve the dispute during school holidays.
"Teachers deserve to return next week and get on with the job," Mr Willie said.
"It's an indictment on the government this has been going on for 12 months. They have the power to solve this."
Mr Willie said the rejection of the offer coming at a time when the government was preparing to cut $450 million from the public sector to meet a budgeted efficiency dividend threw schools into a new level of uncertainty.
"Schools will be in the firing line with what will equate to budget cuts of more than $100 million from education," Mr Willie said.
"Teachers and other staff now face months of uncertainty on top of these failed negotiations by government."