Best Free And Open Source Educational Software For Kids
Tux Paint

Tux Paint is a free and open source drawing program for children. It is very excellent award winning program. It consist of very user friendly graphical user interface desinged for children. It consist of sounds effects and cartoon mascot who guides children as they use the program. Tux Paint provide the very comprehensive drawing tool,it provide very good features to their user like paint brush, rubber stamp, line tool, shape tool, text and label tools ,eraser,undo and multiple levels of undo, undo actions can themselves be undone with the ‘Redo’ button etc. Tux Paint supported cross platform (Mac OS X (10.4 through 10.9), Windows (Windows95 through Windows 8), Linux and other systems).It is released under the GNU General Public License.
Canorus

Canorus is a free and open source music editor tool for children. It supported number of functions like MIDI playback of written notes, import and export filters in numerous formats,import and export filters, staffs and polyphony. Since it is open source therefor its source code is publicly open. You have freedom to change its functionality according to your needs. It is released under GNU GPL license. It can be run on different operating system like Linux, Windows, MacOSX. List of features provided by this software are provide multiple view for different task,provide numerous import possibilities,provide lyrics,translate into different languages,supported standard notation elements,provide undo,redo, copy and past,print preview and many more features.
Childsplay

Childsplay is a free suit of educational games for children. You can used it at home and schools. It is very interesting learning games for young children. By playing this game you learn math,spelling,letters of the alphabet, eye-hand coordination and many more things. It has been released under the GNU-GPL license, and supported different operating systems like GNU/Linux, FreeBSD and the Windows platforms. Childsplay provide number of features to their user some the main features are based on object oriented framework for easy activity development in Python, login facility to monitor the children progress, supported MySQL database, support multiple languages, game activity included puzzles, pong, pacman and billiards, teach the children about the use of mouse and keyboard and many more.