Several people have mentioned that taking a group of Rookies into combat results in lots of dead Rookies. They panic and go berserk with annoying frequency, even if they have maximum initial bravery. If you lose 4 out of 14 rookies, and have no alien kills, then the remainder are ready to bolt.
However, one thing to remember is that higher-rank soldiers give a Morale bonus to all lower-rank soldiers. If the higher-rank soldier is killed, then all lower-rank soldiers will be affected with a big negative to morale. The bonus (and penalty) is greater if the difference in rank is greater.
A Sergeant helps, but isn't quite effective enough. However, if you bring 1 Captain (or even better, a Colonel or the Commander) along with 13 Rookies in a Skyranger, your morale problems are over! The officer stays in the 'ranger, providing moral support and encouragement-via-radio to the rookies (he's a strategic officer, not a field officer). The officer provides several benefits:
--By staying in the 'ranger, the officer can abort the mission if there is a CF/SNAFU/FUBAR situation (choose your acronym).
--By staying in the 'ranger, the officer is unlikely to be killed--thus, the rookies retain their morale benefit throughout the mission.
--Excess weapons, grenades, and such can be left in the 'ranger. Rookies may not have the strength to carry everything. The officer (with a decent level of strength) can throw equipment out of the ranger to rookies in the field.
--The rookies will gain much more experience, as they will make all the shots and all the kills. This keeps your officer from stealing all the experience with her superior skills.
--The officer's skills do not matter in the slightest. This is an excellent position for that "why did X-COM promote that guy again?" officer! Finally, a use for the useless officers!
--By only having one officer, you never suffer morale penalties for losing officers in the field. If you have a Colonel, a couple Captains, four Sergeants, and 7 Rookies, the Rookies will start to panic when you lose a Sergeant or two, or a Captain. If you have one officer, and the officer is alive, you can lose 7-8 Rookies before they start to panic.
The only problem is ensuring the officer survives. If all 13 Rookies are alive and well, but the officer goes down...expect utter chaos. Still, I've found it is a very useful tactic for training Rookies, when I'm trying to get a good second-string Skyranger platoon, experienced base defenders, or a decent selection of replacement soldiers.
Note that you can use this tactic well into the game. 25 Squaddies and 1 Commander who stays on the ship works very, very effectively. The Squaddies in the line of fire won't suffer huge morale losses when their buddies die. In addition, Squaddies in XCOM can (and often do) have better stats than the officers (unless you fire or kill low-stat officers). Basically, the idea is to minimize morale penalties (which occur when soldiers die, so you want low rank soldiers in the line of fire). And, you want to maximize morale bonuses (which occur when officers stay alive, so you want officers to be safe throughout the battle).
--[Zeno] in xcom.co.uk, reposted by JellyfishGreen 15:34, 25 Apr 2005 (BST)