Dress code for women when on campus

Sleeves at least till elbows, and dresses/skirts/trousers till ankles.  This is consistent across all universities in this country.  Plus, the clothes have to be loose, so no figure hugging dresses or trousers, or at least, the strategic areas need to be covered by loose clothing (shirt tail, scarf, shawl, etc).

There is a long multi-page thread about this on www.eslcafe.com , a site that you must register for and then proceed to the International Job Forums, and then to the Saudi board.  Lots of useful info there, and you are guaranteed to get answers quickly if you ask something.  It is a must visit site for any EFLer anywhere, even in general for all teachers.

In Saudi all schools Universities and collages instructors can wear only dark color skirts like blue, brown or black. With quarter sleeves shirt. Nothing much than that. Skirt shouldn't be short in length it should be below kness.
Pants are not allowed any where.
I hope that will be helpful to you.
Good luck for ur new experience.
Regards
Sana

Pants are not allowed any where.

That's not true.  They are definitely allowed in some univrsities, but perhaps not all.

For my place of work, it's ankle-length skirts/dresses (any color or pattern), sleeves below the elbows, zero cleavage and no slacks.  The exception seems to be my Pakistani and Indian colleagues who wear their traditional garb.  It depends on the place of employment and of course, I'm in Jeddah which isn't as uptight as Riyadh.  Anyway, no harm in packing a few pairs of dress pants but definitely bring clothing that fits the above criteria and you'll be fine.  Also, bring along several cardigans, light jackets or sweaters because the air conditioning in classrooms and offices can get quite cold regardless of where you teach.