Youngsters from a variety of county schools gathered in Preston outside County Hall today.
But as today is a normal school day, they should technically be in school, making parents potentially liable for a fine for unauthorised absence.
Preston pupil Martha Amos carried a home made sign at today's demonstration reading "This is more important than my GCSEs".
But it seems that Theresa May does not agree.
A Downing Street spokesperson said: "Everybody wants young people to be engaged in the issues that affect them most so that we can build a brighter future for all of us.
"But it is important to emphasise that disruption increases teachers' workloads and wastes lesson time that teachers have carefully prepared for."
As today is the last day before half term in Lancashire, some schools may take a relaxed approach to their pupils' absence.
But the National Association of Head Teachers, which last week offered some support for those joining the strike, gave a more hard-headed assessment to its members as the day of the action approached.
“Pupils should only be out of school in exceptional circumstances. Whilst NAHT supports the right of young people to express themselves, first and foremost, pupils should be in school during term time,” the union said.
“While a school leader’s role is to ensure children attend school, are kept safe and receive a good quality of education, it is right that individual school leaders can decide how best to respond to any proposed protest by students in their school on Friday.”
Ultimately, the decision is in the hand of each individual headteacher, but unions did not appear sympathetic to the pupils.
Chris Keates, general secretary of the NASUWT teaching union, said young people were right to be concerned about climate change but warned that teachers had genuine safeguarding issues to consider.
“It’s not appropriate for pupils to just walk out of school. The young people organising this are potentially putting themselves and others at risk by simply walking out of school,” Keates said.