February 5, 2014

Exhibit 10.18

February 5, 0000

Xxxxxx X. Xxxxxxxxxxx

Xxxxx Executive Officer

0000 X Xxxxxx XX

Xxxxxxxxxx XX 00000

Re: Collaboration Agreement, dated as of February 6, 2007, by and between The Corporate Executive Board Company and The Advisory Board Company (as previously amended, the “Collaboration Agreement”)

Dear Xxxxxx:

This letter confirms that The Corporate Executive Board Company (“CEB”) and The Advisory Board Company (“ABCO”) have agreed to extend the Initial NP Term and the Initial EC Term (as such terms are defined in the Collaboration Agreement) through February 5, 2017 as comtemplated by Sections 3.3(a) and 3.4(a) of the Collaboration Agreement, respectively, effective as of the date hereof.

Please indicate your agreement with the foregoing by signing and returning one copy of this letter to my attention, which shall constitute CEB’s and ABCO’s agreement with respect to the subject matter hereof.

Very truly yours,

/s/ Xxx Xxxxxxx

Xxx Xxxxxxx

Chairman of the Board and

Chief Executive Officer

ACCEPTED AND AGREED:

THE ADVISORY BOARD COMPANY

By:		/s/ Xxxxxx Xxxxxxxxxxx
		Xxxxxx X. Xxxxxxxxxxx
		Chief Executive Officer