Simmons, a native of Melbourne, Australia, is in his third season in the States, attempting to lead Montverde Academy (Fla.) to its third national championship in as many years.
The Aussie southpaw, a shade under 6-foot-10 and 225 pounds, is rated by Scout as the No. 2 player in the country and is the most celebrated Tiger basketball signee Shaquille O'Neal.
He recently led Montverde to a title in the AllState Sugar Bowl National Prep Classic on the Westbank of New Orleans and, afterward, spoke with reporters about playing in Louisiana and getting to LSU.
Blakeney, 6-foot-4.5 and 170 pounds, is Scout's fifth-best shooting guard in America and ranked 22nd overall in the 2015 class.
Their selections Wednesday mark the first time since 1993 that LSU has had two players in the same year make the prestigious all-star game.
In that year future Tigers Ronnie Henderson, Randy Livingston and Sylvester Ford appeared in the game, although Ford didn't start his career in Baton Rouge, instead transferring in from Memphis.
Another time, in 1988, former LSU coach Dale Brown had a pair in the McDonald's All-American Game in big man Stanley Roberts and perimeter scoring phenom Mahmoud Abdul-Rauf, formerly Chris Jackson.
The 2015 McDonald's All-American Game will be played in Chicago's United Center on April 1.
Both Simmons and Blakeney will play for the East team.
PREVIOUS MCDONALD'S ALL AMERICANS AT LSU
2013 - Jarell Martin (Baton Rouge, LA)
2011 - Johnny O'Bryant (Cleveland, MS)
2005 - Tasmin Mitchell (Denham Springs, LA)
2004 - Glen Davis (Baton Rouge, LA)
2003 - Brandon Bass (Baton Rouge, LA)
1998 - Stromile Swift (Shreveport, LA)
1993 - Sylvester Ford (Memphis, TN - Transferred to LSU from Memphis)
1993 - Ronnie Henderson (Jackson, MS)
1993 - Randy Livingston (New Orleans, LA)
1992 - Duane Spencer (New Orleans, LA)
1990 - Jamie Brandon (Chicago, IL)
1989 - Shaquille O'Neal (San Antonio, TX)
1988 - Stanley Roberts (Hopkins, SC)
1988 - Mahmoud Abdul-Rauf (Gulfport, MS)
1984 - John Williams (Los Angeles, CA)