Sigh... higher education includes university and TAFE. I assume TAFE/trades would come under the "Skills" portfolio & universities under the "Innovation" portfolio.
Regardless, when policies in these areas are brought to Cabinet, all three Ministers will attend the Cabinet Meetings to debate & approve the policies.
There is also phones & internet which will allow their departments to consult on matters that cross the three portfolios.
Education is a massive policy area. One would think 3 heads are better than 1.