Some programs have a virtual on-screen keyboard like Click-n-Type which is free. Click n type has a word prediction feature built in (a separate downoad from the keyboard) that will give choices to select to cut down on the amount of typing.
A powerhorse program that does all of the above and has a text to speech feature as well is Co:Writer by Don Johnson. This program opens a text writing window that floats above a MS Word document or whatever word processing program you want to use. As you type, you get word prediction underneath and when you type a period, the sentence is transported up to the word processing page. You also hear it read back to you. You can turn the speech off if you prefer and you can set the size of the text window, the number of words in a prediction list and how you want to select them.
There are other features like word banks under topics to load as a source for word prediction that make this an excellent program. At $325.00, it is a spendy tool, but if you want or need to write or want to find a support for your child to do homework assignments and papers on a computer at home, it is a worthy investment.
Check these out.
All the best!