Laura Freschi makes it, citing work by William Easterly and Yaw Nyarko.

Even using official figures, which likely far undercount the value of remittances by excluding informal channels, remittances sent back by Africans abroad outweigh the cost of educating them at home. Why pass up a high return opportunity (Africans earning high incomes abroad and remitting) and insist on a low return activity (educated Africans underemployed at home)?

I could probably link to the Aid Watch blog three or four times a week. I strongly recommend making it a regular read.