The youngsters wriggled in their seats as the men stood before them.
One said she had “never seen a full naked man before”.
Amelia, 14, said it was “just a lot of naked men in real life to process.
“We’ve never really seen it!
“It’s interesting to see how the same thing can look so different.”
They also discussed the average length of a flaccid penis in the UK (about 3 inches, or about 7.5cm) and why one of the men was circumcised.
Other episodes have shown women’s bodies, and disabled bodies and also discussed body hair. An upcoming episode will feature two transgender men.
Some critics have labelled the show “gutter TV”. They have argued that the nudity is unnecessary and “tacky” and have questioned whether it was legal.
Other criticism has come from commentators on the right of British politics who often wade into “culture war” issues, such as former actor Laurence Fox.
Supporters of the show have praised it for tackling difficult issues with sensitivity and accused critics of sexualising it, with many commenting that they wished there had been a similar show when they were younger.
Presenter Anna Richardson, who also hosts Naked Attraction, said the show was “educational, emotional, joyous”.
“Naked Education is one step further than Naked Attraction,” she told The Sun.
“I like to make shows that are controversial, that break taboos and that make a difference, and with every single show that I’ve done you can tick one of those boxes.
“Naked Education is a body-positive, educational series that is basically aiming to normalise all body types and champion everybody’s differences, so that we can accept that with our clothes off we’re all normal.”
A Channel 4 spokesperson told the Daily Mail that all the teenagers in the show participated with “appropriate consent”.
“They and their guardians were fully aware and prepared to take part in the item about body taboos and they all had support throughout.”
