IMHO using "wo" here is colloquial in the sense of "being unprecise with language". It is possible to use "wo" to start an adverbial subclause qualifying a point in time. @Grantwalzer and @Hulk contributed the corresponding Duden entry, and @Alexander Kusobek this related question where @tohuwahohu did a fine job compiling many examples from German literature for this way of using "wo".
In the given article, however, "wo" is not used in an adverbial way. The subclause
wo mehr als 70 Prozent eines Jahrgangs eine akademische Karriere anstreben
does not qualify further "heute", but gives a reason for why very different challenges arise. The article also says that they arise today, but this general present is not better described by the subclause.
The easiest way to fix the phrase is replacing "wo" with "da". According to the corresponding Duden entry it is used to denote a temporal, but also causal relationship, and thus matches exactly the situation we are facing here. Also note the example from the Duden
jetzt, da es beschlossen ist, kommt dein Einwand zu spät
which has exactly the same structure.
As an alternative, one could write "... heute, in einer Zeit, in der ...", but this is more complicated to read; I would only consider it if I really wanted to have that break created by the insert.
Or, as @Kitana suggested
Da heute mehr als 70 Prozent eines Jahrgangs eine akademische Karriere anstreben, stellen sich [X] ganz andere Herausforderungen.
which makes the causal relationship even clearer. I would consider inserting an indirect object at [X] then; otherwise I had the feeling that something is missing there.