Establish/Maintain a Formal Argument Style Practice Test

A student writes the following in an argumentative essay about later homework deadlines: “No one disputes that teachers assign way too much homework, and it ruins students’ lives.”

What is the primary formal-style weakness in this sentence for an academic argument?

A student includes the following lines in a formal letter arguing for more library funding: “We request an increased library budget because updated nonfiction texts support research skills. Also, the library is kinda sad right now and students hate it.”

Which revision best fixes the inconsistent style while keeping the meaning?