Pupils will now only be authorised to miss school to go on climate strikes once a year, after a controversial decision by City of Edinburgh Council.
Activists have vowed to "keep challenging" the limitation after a meeting of the local authority's education committee today.
Pupils had previously been turning up to protest outside the Scottish Parliament on an ad hoc basis, with permission first granted by the council in March. Edinburgh was the first local authority in Scotland to make such a move.
One head's message to students: Join the climate strike
Now, absences to protest that are not part of the agreed day off during the academic year will be recorded as unauthorised, with "parental consent" required. Eight councillors voted for the motion, while two – both Greens – voted against.
More action is planned by the Scottish Youth Climate Strike (SYCS) group on 20 and 27 September as part of what has become a continuing global movement started by 16-year-old Greta Thunberg.
Sandy Boyd, of SYCS, said after the meeting: "It's a little disappointing, but they have given us permission for one strike a year.
"We will keep striking no matter what and we will keep challenging the council on this."
Thousands of children previously descended on the Scottish Parliament building in March and May along with fellow pupils in more than 100 towns and cities across the UK. Smaller groups have been gathering at the parliament every Friday since January.
Edinburgh Council education convener Ian Perry said: "We support the young people making their voices heard regarding climate change as it is one of the most important issues that's facing the world.
"However, there needs to be a balance struck and if we allow pupils more than one absence the issue is that they could be regularly missing school, which affects their education.
"We are also encouraging schools to support pupils in any projects that help educate them in school about climate change."
Before today's meeting, Green MSP Ross Greer said: "Instead of treating these young people like truants, Labour and SNP councillors need to start listening to them.
"They must recognise that school pupils have been forced to take this action by the failure of previous generations to stop the climate crisis.
"Green councillors made sure that Edinburgh led the way on supporting the first school climate strikes this year."
Mr Greer added: "Instead of taking this backwards step, the council should recognise that these actions are not only admirable, they are entirely in keeping with the Curriculum for Excellence and the objective of developing responsible citizens.
"We are in a climate emergency, with the UN giving governments just a decade to turn things around.
"Clearly our leaders need to educate themselves on the facts before deciding whether taking this vital political action damages the education of our young people."
Earlier this week, SYCS organiser Dylan Hamilton, 15, said: "Allowing us to protest once a year is simply not acceptable and will not let us get across how serious this is to the people in power.
"Our classic education, such as preparation for exams, may suffer because of the strikes. However, by striking we learn politics, organisation, science, independence and more about society than we've ever been taught.
"To say we are harming our education is untruthful.
"Furthermore, punishing pupils for attending the climate strikes is a violation of our human right to freedom of expression."