The Socialists, led by Prime Minister Antonio Costa, won an outright parliamentary majority in an election a year ago but the government has had a bumpy ride since then, with 13 ministers and secretaries of state leaving their roles, some over allegations of past misconduct or questionable practices.
"It would be good for the leaders who are watching this demonstration to think very carefully about what they are going to do next because we want this to have consequences; we want serious measures to be taken," said maths teacher Aitor Matos.
The 47-year-old said teachers were "constantly losing income" and were often placed in schools far from home.
Protesters, some wearing black to mourn the state of the education sector, said the government has done little to improve their situation.
"We have to be respected," said special needs teacher Lucinda Lopes, 52. "They must give us what is rightfully ours and they can't take away the little we have."
Teachers across the country have been on strike since early December, leaving many students unable to attend lessons. The education minister said on Friday he might force some teachers back to work by decreeing minimum services.
