Why only ketone forms enolate in Claisen condensation between ester and ketone? Claisen condensation involves nucleophilic substitution in esters by an enolate (formed by removing an alpha-H from an ester or a ketone) giving a beta-keto ester or a diketone. 

My textbook says that for the reaction between ketone and ester, the ketone always forms the enolate by losing it's alpha-H . But why can't the ester form the enolate here? What will happen if the ester has alpha-Hs and the ketone dosen't?

Attempts:

Does it the O on the alcohol side of the enolate ester help in delocalizing the negative charge via an inductive effect making it less effecive as a nucleophile?

(I can't find anything on other sites I've seen:

http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch21/ch21-3-3.html

https://en.wikipedia.org/wiki/Claisen_condensation

http://www.chtf.stuba.sk/~szolcsanyi/education/files/Organicka%20chemia%20II/Prednaska%205_Aldehydy%20a%20ketony_Reakcie%20II/Doplnkove%20studijne%20materialy/Carbonyl%20compounds_full_Blackmond.pdf

https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Reactions/Organic_Reactions/Claisen_Condensation )
The pKa of a ketone alpha hydrogen is of the order of 20, the pKa of an ester alpha hydrogen is of the order of 25 source. Bear in mind that this is a log scale, meaning the proportion of ketone enolate to ester enolate is 100000:1.

In answer to the comment by @orthocresol: the ketone does self-condense, but this is reversible. The condensation with the ester is irreversible due to formation of the anion of the product B-diketone.