Which excerpt from a student essay is more formal?
In this day and age, nearly all classrooms have access to technology. A lot of kids use computers at school nowadays.
Informal writing is typically used in casual situations or when communicating with someone you know well. Informal language often expresses familiarity and tends to sound more like speech. It uses more conversational language, such as slang, idioms, abbreviations, imprecise language, and contractions.
Formal writing is typically used in academic and business writing or when writing directly to an authority figure. It tends to be more courteous and impersonal, avoiding overly familiar or conversational language.
Compare the following sentences.
Informal: Yeah, ostriches can't fly, but I think they're awesome.
More formal: Ostriches may be flightless, but they're remarkable runners.
Most formal: Though flightless, ostriches are remarkable runners.
The first excerpt from a student essay is more formal. It uses more elevated language (in this day and age, have access to technology). The other excerpt uses imprecise language (a lot, nowadays) and sounds more conversational.