Allow me to explain. I am a new DM figuring out 1e for a group of players. Some of them have expressed their desire to play classes that are difficult to roll the criteria stats for, like the paladin or the monk. Is there a way I can satisfy the game's rules and allow them to play these classes? It's likely they will be unable to qualify with their dice rolls, after all. I'd like to retain the fair feel of the character-creation process, however.
The AD&D Dungeon Master's Guide provides alternate methods of generating ability scores on page 11 under the heading Creating the Player Character. Some of these produce much higher average results than others. But it sounds like ability scores have already been generated.
AD&D Is Fair as Written
That isn't a lot of fun, though.
But one of the premises of AD&D is that you're supposed to play what you roll. If you roll poorly you're playing a fighter, and if you roll well you're playing a paladin or ranger. If your fighter dies, you take out another index card and roll up another character. Low-level characters with low ability scores in AD&D are disposable, and monsters will eat them, and then you'll get a new character who might be more survivable, who has better ability scores and a better class.
And if that character with a bad class and bad ability scores, through luck, skill, cowardice, strategy, and more luck, actually survives long enough, how he did so are stories you can tell.
That how is the fun.
I don't know in which edition they introduced alternative dice-rolling methods but it sounds like this is what you're looking for.
In ADND-2E the main method is to roll 3d6 and assign it to the first ability. Then the second 3d6 go to the second ability; and so on.
The alternative methods listed in ADND-2E are:
Other alternatives I've seen (can't recall where) are:
If you go for the point-buy (pool of 80), I'd suggest you don't let them have scores of 3 either... go maybe up to 6 for minimum.
Of course, you can mix-and-match as you like. I usually let them roll 4d6 six times and assign as they want. Their characters may be a bit higher-than-normal, but as a DM you should be able to balance it.
Each method proves to be fun in some way or another; but for new parties, I'd let them have some sort of control over the rolls they choose. IMO, it lets them grow fondness for their PC.
As others have noted, the default assumption of AD&D 1E is everyone is going to play based on what they roll. It's worth noting though, that very old D&D/Chainmail assumed each player had multiple characters, so odds were you probably had 1 special type out of the bunch.
That said, one alternative rule you could do is let the players bring their characters up to minimum stats to play a class, for a one time XP debt - for example, maybe they have to pay off 1,000 XP before they can earn XP normally. This will put them about 1/2 a level behind everyone else (well, sorta, 1E classes level differently by the class), while still letting them have the classes they want.