Hello, stoopib. I don't have time to analyze it all, but I'll try to point out a few things you've missed.
"Ego discipulos in scholis stultissimos fieri puto, quod nihil, ex his
quae in usu habemus, aut audiunt aut vident, sed homines plenos timoris
petentes a piratis ne se in catenas iniciant, sed tyrannos edicta
scribentes quibus imperent filiis ut capita patrum suorum praecidant,
sed reges oraculis monitos ut virgines tres immolent ne pestilentia
gravior fiat...
I reckon students experience the most foolish things in schools, because they never hear or see nothing we use, but instead become men full of fear of pirates for not to fall into their chains, but they become tyrrants who writing their decrees command children to cut off the heads of their parents, but they become kings respecting oracles and sacrificing 3 virgins so a more serious plague may not happen..."
Careful attention to adjective agreement will fix your translation here.
discipulos and
stultissimos agree. I don't see a verb that could mean "experience," but
fieri means "become." Try putting those together. Notice also that
homines plenos,
tyrannos, etc are in accusative case. They are to be contrasted with
nihil, which the
sed indicates. (I think you might have imported
fieri from the first clause. So try: "they never hear [about] anything. . . but [or except] men. . ."
Qui inter haec aluntur non magis sapere possunt quam bene
olere qui in culina vivunt!
The ones who grow up in the kitchen have good sense and even smell better (THIS CONFUSES ME TO NO END!).
It's a bit tricky, I admit. You haven't included "inter haec aluntur" in your translation, though. Let me clarify it.
[Ei] (=qui inter haec aluntur) non magis sapere possunt quam [ei] (=qui in culina vivunt) bene olere [possunt].
Think of
qui inter haec aluntur as the subject of the sentence, with an implied "the ones" (as you know). "Non magis sapere possunt" might be rendered "are no more able to have good sense [than...]."
Just a few comments on the rest.
Levibus enim atque turpibus declamationibus
magistri effecerunt ut corpus orationis enervaretur et caderet. Certe
neque Plato neque Demosthenes ad hoc genus exercitationis accessit!"
Non est passus Agamemnon me diutius orare: "Ego magistros fateor in his exercitationibus peccare, sed debemus eis ignoscere. Nam nisi dixerint ea quae adulescentibus placent, ut ait Cicero, 'soli in scholis relinquentur.' Parentes culpa digni sunt, qui nolunt liberos suos severa lege discere. Nunc, ut puero, in scholis ludunt; ut iuvenes, ridentus in foro."
"Agamemnon suffered for a long time to reply"
-
passus est normally means suffered, but does this fit in the context? Another meaning is "allowed." Also, what do you do with the
me orare? Note that
patior, like
sino (to allow), can take an accusative infinitive construction. Thus: "Agamemnon did not allow me..."
"'they would become accusted to being left behind in school'"
-it's
soli, not, as I'm guessing you thoght,
soliti. Try: "they will be abandoned alone..."
but here it goes.
positive, negative... get it?) of 
