Why is Pip dissatisfied with Mrs.Wopsle's school?

After Pip becomes old enough in Great Expectations, he is to be apprenticed to Joe. In the meantime, he is given various and sundry little tasks around his home and that of the neighbors. In the evening, Pip attends an evening school, in the village; this school is purportedly run by the great-aunt of Mr. Wopsle, the church clerk. Dickens satirically describes her,

She was a ridiculous old woman who used to go to sleep from six to seven every evening in the society of youth who paid twopence per week each for the improving opportunity of seeing her do it.

However, it is really the granddaughter of Mr. Wopsle's great-aunt, an orphan, who teaches Pip. For, the "educational scheme" of Biddy's grandmother has these flaws:

The students eat apples and put straws down each other's backs until the old woman tries to strike them with a birch stick.

There is only one book from which the children can learn, and they must pass it back and forth.

While the book is passed, Mr. Wopsle's great-aunt falls asleep, so no learning takes place.

Then, the students return to teasing each other by stepping on one another's toes.

After this occurs, Biddy rushes at the students and distributed three "defaced Bibles" which are so moulded and rusted that little can be gleaned from them.

Some of the students rush at Biddy and she has to combat them. Undaunted, little Biddy reads aloud and has the other recite, but they know little of what they have read. So, later, Pip asks Biddy to tutor him because he really wants to better himself in hopes of being worthy of Estella by becoming "uncommon." Every evening Pip and Biddy meet to discuss prices, read, and copy letters.