Try teaching them to read phonetically. A good way is combining phonetcs and whole word lreaning to read method. A good book can be found at www.readinglesson.com They also offer a lesson or two for free. It really works even with older students. Book has been designed for those experiencing difficulties learning to read. 

Also try  searching mini-books of David Lisgo, a member of this site. Type his name in the "by the user" section.

On youtube search for phonics from MapleLeafHashima youtube channel, Koomakids and there should be others.

Start by teaching them each letter sound, go on to the long and short vowel sounds, and then diagraphs and triagraphs. It �s also good to work on memorizing the common sight words.

You also have to work on their ability to hear the first last and middle sounds in easy words. P-I-G for example. The first sound is the easiest for kids to hear, then last, then middle. Focus on vocabulary and naming the first sounds. Once they can do that, work on last, then finally middle sounds.

Then comes the next step, using these skills to actually sound out words. I have them cover the letters in the word and make the first sound. "P", then move the ruler (finger, pointer) and sound the second letter "I", then the two together " Pi"... and so on.

Discourage guessing, and have them go through the letters sounding them out until they say the word and know what it is. If you stand over them and make them sound each sound out like this, and push hard for them to not guess, and finish each word... for a week or two, then they will do it on their own, with only a little guidance and reminders not so guess.