Whenever any school district shall select any real estate as a site for a schoolhouse, or as additional grounds to an existing schoolhouse site, within the district, and the board of school directors of such district and the owner or owners of the site or any part thereof, or addition thereto selected, shall be unable to agree upon the compensation to be paid by such school district to the owner or owners thereof, such school district shall have the right to take and acquire title to such real estate for use as a schoolhouse site or additional site, upon first paying to the owner or owners thereof therefor the value thereof, to be ascertained in the manner hereinafter provided.