I went on a school cruise when I was 13 (1988). It was run by Schools Abroad and it was the SS Jupiter. The ship sunk exactly a year later in Piraeus Harbour.
Having said that, the cruise was a fantastic experience. We flew to Turkey and sailed to Rhodes, then Israel (visited Jersualem, Bethlehem & Dead Sea in one day), and then Egypt (saw Nile, Pyramids, Cairo & British Museum, ending at Port Said) another day. Then returned to Greece, visited Athens & flew home.
It gave me a life long love for the Middle East - still my favourite holiday destination - and I appreciate how lucky I was to visit these ancient historical cities / sites / buildings, especially when they are now, again, the scene of fighting and bloodshed.
I agree with those MN'ers who have commented on the things which make you cringe now when you think back. The Arabs at the pyramids were a little frisky (!) and I was somehow able to wander around the market in Port Said - Cairo's port - on my own, buying leather bags as gifts.
Safety seemed fine on the ship but no harm in making sure your DS thinks about safety(without scaring him) -
i'l have a think about any other tips (which I think would mainly apply to girls) - and will write back
the main tip is - it's a wonderful experience & i'd recommend it to anyone