Okay, not terrible. Not great... but not completely awful.

Here are my suggestions for improvements.

1) There is no big score here. Players will hate this dungeon. [-10 points]

2) The hook is lame. It is written as if there are not six other far more exciting things going on in the campaign that the players would rather do. [-10 points]

3) The wandering monster table has a huge error-- it places "monster + treasure" densities of kobalds and xvarts just wandering around in the fields. THIS MAKES NO SENSE. (The numbers need to be in the 5-7 range-- just scouting parties that will likely attempt to run back to the lair at the first sign of trouble. [-10 points]

4) The haunted cornfield is just a bit much and you can already see your commenters suggesting that it simply be burned down. The idea of the players making their own passages out here just seems... really unworkable. [-10 points]

Oh. Whoops. That is only 60%. A failing grade. But look how easy the fix is!

1) Add an access point down to level four of the dungeon. It is a *long* vertical shaft and it goes long enough that the players will be clued in that something nasty down there. There was a cave in on the fourth level of the dungeon. At the bottom of the shaft is the lair of a carnivorous ape which includes 3000 electrum and 1000 gold. Switch the monster encounter chart to a d12 and make the ape the #12 result. If he appears, he will stalk the party and attempt to kidnap someone Predator-style in order to eat them. He is smart enough to wait for the PC's to get their nose bloodied fighting something else. If the players rappel down the shaft and get the gold... be sure to track all of the gear that has been taken down there from the victims over the course of the game. (The "pot" keeps getting larger; this would be a good deal in a multi-party / open table setup.) Note that getting the treasure up the shaft is also a problem. Also, the players can with time open up a passage into the mazes on level four of the dungeon. (Well dang. I just put more effort into this one room than you did on your whole dungeon!)

2) It's an old stand by, but there is an evil cult made of normal humans led by a second level cleric that has the scarecrow spell. Going with a Children of the Corn theme here because you started it. Dead PC's that do not get a proper burial are collected and converted into this new undead type. (Replace the deer encounter with a 3 of these... preferably with people that party would know.) Add a Stone Henge type area on a hilltop and only have the cultists engaged there on particular nights... call it one-in-eight rolled at the start of each session. Replace wild boars encounter with a group of ten cultists moving through preparing for an upcoming sacrifice. The cult leader should be played intelligently. He has an elaborate piece of cursed jewelry that should be worth 10,000 gold, but whoever picks it up will start hearing the voice of some elder god. (Tell the player secretly about all this. Whoever touches it first will become possessive of the item and will actually get the 10K of XP when he takes this back to town. But he won't find a buyer and if they other PC's don't take the initiative to try to find some kind of remove curse or something, then this guy will become the new cult leader during his downtime actions.) The hook to get the players to investigate the area is some guy with no money begs the party to retrieve his daughter. All he can offer is her hand in marriage which... once effected would hand him over a modest estate. The twist is that the girl has totally drunk the Kool Aid as it were. (An estate is too nice of a reward for a level one adventure scenario.)

3) Instead of 6-18 kobalds, make it just 6. Instead of 6-15 xvarts, make it 8. (I blame Moldvay Basic for this terrible errors of yours, but dang. I don't see why people don't call this out as an obvious problem. The random wandering monsters are not full on mega-battles. They are there as a resource drain on time wasters and also to add additional hazards to parties that have lost PC's and are trying to get out of the dungeon.

4) Okay, look. Just make it a cave already. And the size of this map is too small to be "Jaquayed". You should be embarrassed to be throwing around terms like that. People like you that think you are smart for repeating OSR jargon of that sort should go back to OD&D and just do Gary's advice for starting with a map of the dungeon from the sideview first. This is where the twisty maziness really occurs. Think of a dungeon level as a place where there are several things going on at once and make it possible for the players to select a target to focus on out of half a dozen options... which is about what we have attained at this stage. If can't be linear. There has to be more than one thing going on. It has to be possible for players to focus on something that THEY are especially interested in.

Okay, that was way harder to fix than I expected. So you *DO* deserve your grade of "F".

I don't see any intelligent comments on your piece so far. Very disappointing. It is weird to me why my suggestions here are not immediately obvious to the peanut gallery.

If you want to get better as a dungeon designer, then go ahead and make a one page level 2 xvart dungeon that has more rooms than this. Also a level 3 kobold dungeon. And then make that sideview sketch of how everything stacks up on top of each other. Players are likely to assume that either place is "the" dungeon when they find it, so you need to have that before you run this.