set s1 to "echo A"
set s2 to "echo A"
tell application "Terminal"
    activate
    tell window 0
        set visible to true
    end tell
    set shell to do script s1 in window 0
    tell window 1
        set visible to true
    end tell
    set shell to do script s2 in window 1
end tell

tell application "Terminal"
    activate
    do script "echo A"
    do script "echo A"
end tell