Exhibit 10.15**EIGHTH AMENDMENT TO LEASE AGREEMENT**     **THIS EIGHTH AMENDMENT TO LEASE AGREEMENT**(this “**Amendment**”) is made as of the 21st day ofFebruary, 2007, by and between **1899 L STREET TOWER LLC**, a Delaware limited liability company(“**Landlord**”), and **BLACKBOARD INC.**(“**Tenant**”).**W I T N E S S E T H**:     **WHEREAS**, 1899 L Street LLC (“**Original Landlord**”) and Tenant entered into that certain OfficeLease dated November 22, 1999 (the “**Original Lease**”), as amended by that certain Amendment to LeaseAgreement dated February 16, 2000 (the “**First Amendment**”) as further amended by that certain SecondAmendment to Lease Agreement dated July, 2000, as further amended by that certain Third Amendmentto Lease Agreement dated January 31, 2001 (the “**Third Amendment**”), as further amended by thatcertain Fourth Amendment to Lease Agreement dated March 22, 2002 (the “**Fourth Amendment**”), asfurther amended by that certain Fifth Amendment to Lease Agreement dated August 31, 2005, executedby Landlord (as successor-in-interest to Original Landlord) (the “**Fifth Amendment**”) as furtheramended by that certain Sixth Amendment to Lease Agreement dated January 20, 2006 (the “**SixthAmendment**”), as further amended by that certain Seventh Amendment to Lease Agreement dated November3, 2006 (the “**Seventh Amendment**”; all of the foregoing being collectively, the “**Lease**”) pertainingto 62,665 square feet of space (the “**Premises**”), including the 500 square feet of storage spaceleased by Tenant pursuant to the Original Lease, the 700 square feet of storage space leased byTenant pursuant to the Second Amendment and 646 square feet of storage space leased by Tenantpursuant to the Sixth Amendment (collectively, the “**Storage Space**”) located in that certainbuilding (the “**Building**”) located at 1899 L Street NW, Washington D.C.; and     **WHEREAS**, Landlord and Tenant have agreed to amend the Lease, as more particularly set forthbelow.     **NOW THEREFORE,**in consideration of the covenants contained herein and other good and valuableconsideration, the receipt and sufficiency of which is hereby acknowledged, Landlord and Tenanthereby amend the Lease as follows:**A G R E E M E N T**     **1.**     **Amendment**. Section 2 of the Seventh Amendment is hereby deleted and replaced with the following text:2.     First Renewal Option. Tenant, at its option, may extend the Term ofthis Lease for a period (“**First Extended Term**”), commencing on February 1, 2008 for up to three months as indicated below. The option for suchextension may be exercised by Tenant giving up to two written notices (the “**WrittenNotices**”) thereof to Landlord, the first of which
 

 
shall be delivered not laterthan February 23, 2007, provided that at the time of either notice Tenant shall notbe in Default in the performance of any of the terms and provisions of this Leasebeyond any applicable grace periods. The first Written Notice shall extend theLease by one month and 15 days (to March 15, 2008). The second Written Noticeshall extend the Lease by an additional one month and 15 days (to April 30, 2008),provided that no second Written Notice may be delivered after March 30, 2007 or ifthe first Written Notice was not timely delivered. The length of the FirstExtended Term shall be three months if both Written Notices are timely deliveredand shall be one month and 15 days if only the First Written Notice is timelydelivered. The First Extended Term shall be on like terms, covenants, agreements,provisions, conditions and limitations as are contained herein, except that therental payable by Tenant during the First Extended Term shall be equal to$212,866.50 per month ($42.00 x 60,819 / 12) for the Premises, other than theStorage Space (the Premises less the Storage Space is the “**Office Space**”), plus$3,230 per month ($21.00 x 1,846 /12) for the Storage Space.     **2.**     **Façade Work**. Tenant is aware that Landlord is contemplating performing certainfaçade work to the second floor of the Building. Tenant grants Landlord the right to enter theportion of the Premises on the second floor of the Building in order to conduct architecturaldesign work and planning provided that Landlord uses reasonable efforts to minimize the disruptioncaused by such activities.. With Tenant’s written consent, and in no event earlier than four (4)weeks prior to the end of the Lease, as extended, Landlord may perform work requiring access to thePremises provided that such work does not require Tenant to relocate occupants of the affectedportion of the Premises. During all such times, Landlord shall use all reasonable efforts tominimize any interference with Tenant’s use or occupancy of the Premises. Landlord may not, duringthe progress of such work, close or suspend operation of entrances, doors, corridors, elevators orother facilities except as such activities are consistent with the Landlord’s obligations under theLease and would not impair Tenant’s use or occupancy of the Premises.     **3.**     **Broker Warranty** Landlord and Tenant each warrant that it has had no dealings withany broker, agent or any other person in connection with the negotiation or execution of thisAmendment other than Studley, Inc. and Transwestern Commercial Services (collectively, the“**Brokers**”). Landlord and Tenant agree to indemnify and hold harmless the other from and againstany and all cost, expense, or liability for commissions or other compensation and charges claimedby any broker or agent (other than the Brokers) with respect to this Amendment on account of theacts of the indemnifying party.
 

 
     **4.**     **Definitions****.**Unless the context otherwise requires, any capitalized term used herein shall have itsrespective meaning as set forth in the Lease.     **5.**     **Integration of Amendment and Lease****.**This Amendment and the Lease shall be deemed to be, for all purposes, one instrument. Inthe event of any conflict between the terms and provisions of this Amendment and the terms andprovisions of the Lease, the terms and provisions of this Amendment shall, in all instances,control and prevail.     **6.**     **Counterparts**. This Amendment may be executed by each of the parties hereto in separate counterparts andhave the same force and effect as if all of the parties had executed it as a single document.     **7.**     **Ratification**. Except as modified herein, all of the remaining terms and provisions of the Lease shallremain in full force and effect.     **IN WITNESS WHEREOF**, Landlord and Tenant have duly executed this Amendment as of the day andyear first above written.       **LANDLORD:**