Ross Greer, Scottish Green Party MSP for West Scotland, described universities running consent workshops explaining the concept to students aged 18 and 19 as “terrifying”.
“Teaching children about relationships and not including consent is completely bizarre.
“There are also particular pressures pupils face today, such as sexting,” Mr Greer said.
“I believe that by equipping children to understand and talk about consent we will be better placed to tackle rape culture and misogyny towards women in particular.”
Mr Greer said with the age of consent in Scotland being 16 pupils should be taught about consent before they leave school, ideally no later than the first year of secondary.
Mr Greer added: “But the core issue with personal and social education is that it’s completely inconsistent.
“Some schools design their own, some bring other in to design it but there is a substantial number of pupils not getting consent education.
“We as a society are finding it easier to talk about sex and with these societal changes we need to update sex education.”
Sandy Brindley, national coordinator for Rape Crisis Scotland, whose organisation has taken its Prevention Programme discussing issues such as consent, social media and pornography into a third of Scotland’s schools, said: “People still do not understand what the definition of rape is and need to understand consent and what the law says.
“Pupils tell us how much pressure they are under to have sex, watch porn and to obtain and share intimate images.
“Sometimes we’re asked to go into schools after an incident such as sexting and pupils and teachers tell us they appreciate our specialist knowledge. We are well placed to cope if a pupils makes a disclosure to us and know where to refer them.
Ms Brindley added: “I do think this subject is best taught by an outside agency but this then becomes a matter of making sure the finance is available.”
A Scottish Government spokeswoman said: “Scotland does not have a compulsory curriculum in our schools. It remains an important principle that teachers and educationalists – not politicians – should decide what is taught in Scotland’s classrooms.
“Relationships, sexual health and parenthood education is, however, already an integral part of the health and wellbeing area curriculum in Scotland.”