Teenagers say sex education in schools is inadequate, uses ''scare tactics'' and focuses too much on biology instead of issues such as the emotional challenges of relationships, sexual pleasure and consent.

Almost half of year 10 to 12 students believe the instruction they received was either irrelevant or only somewhat relevant to their lives, with one in 10 saying they had received no sex education at all.

Some complained of a ''tick the box'' approach, as teachers rushed through classes, fixating on how not to get pregnant or catch a disease, and giving little advice on navigating sexual relationships in the modern age.

Many felt the system was designed only for heterosexual students, with 66 per cent of those polled in the 2013 National Survey of Australian Secondary Students and Sexual Health, saying the teaching provided virtually no information for gay and lesbian young people.

The survey found that six per cent of students are attracted to those of the same sex, and 11 per cent expressed attraction for both genders. In 2008 only 1 per cent of students identified as same-sex attracted, suggesting young gay people feel more comfortable coming out.

Respondents said sex education should reflect sexuality diversity. One said: ''My school didn’t talk about safe sex for lesbian, bisexual, gay and transgender people, and as a result I know a few same sex attracted girls who are under the impression that they don’t have to worry about getting STIs (sexually transmitted infections) from having sex with other girls.''

Another said the teaching was, ''done through more of a biological lens and taught us about STI prevention and anatomy but did not include important topics such as communication with partners, different relationship dynamics, unusual circumstances or actually getting pleasure from sex''.

Lead author Anne Mitchell from La Trobe University said that given the study showed 43 per cent of teenagers were getting their sexuality information from school sex education classes, it was important the teaching was delivering a broad spectrum of advice, not just information on sexually transmitted infections. However, she said it was concerning that while only 2.5 per cent had been diagnosed with an STI, many were still not using protection.

Forty-one per cent of young people did not use a condom when they last had sex, compared to 31 per cent in the 2008 poll. However, when condoms were readily available 86 per cent of sexually active students said they used them.

''One of our main aims is to get kids having safe sex, this is an ongoing concern but if condoms were more readily available for young people condom use would be higher so we need to look at them being available in the family home and in schools and youth health clinics, particularly rural kids who often have quite a lot of trouble buying them in local outlets,'' Professor Mitchell said.

Students gave their feedback either through an online or printed survey. One student said of their sex education: ''It was basically scare tactics - ‘why not just wait? If you don’t you’ll get diseased and die.''

Another said: ''All of the information I have found has not been through school. Nothing on sexuality, pleasure, contraception other than condoms/the pill ... I had to research everything myself so that I didn’t end up pregnant, diseased or in serious pain.''

One in five said they did not receive enough information on the importance of consent in sexual relationships.

The finding comes after The Sunday Age last month revealed educators and researchers want a radical overhaul of Australia’s sex education system, saying it is leaving young people ill-equipped to negotiate the complexities of sexual relationships.

They called for more information on consent, pornography and sexting to help teenagers deal with the modern sexual environment.