review ___ (prepostion!)

Review as a verb does not take a preposition
e.g. review the proposal

The preposition "on" usually follows "review" when it is used as a noun followed by an object.
e.g. take a review on the proposal

Back to your question. The object of the verb review is "That", not education reform. Without knowing the context, we cannot tell what "That" refers to but we know that it is related to education reform.

There is definitely a preposition but the choice of the proposition conveys different meaning to the sentence.

For example, the context is about public funding for schools. The sentence may read like this:

Public funding for schools is what you want to review in the education reform.
(public funding to schools in the education reform)

Public funding for schools is what you want to review on education reform.
(on the subject of education reform)

Public funding for schools is what you want to review about this education reform.
(concerning the education reform)