How are their handwriting skills?
I've come across older students who'd been studying English for ages , yet were still moving at a snail's pace. After some initial observation, I'd realized that they couldn't write efficiently! Not only had they never learnt strategies for quick handwriting, such as joined Italic, but couldn't even write their basic letters properly (e.g. clockwise 'a's and 'o's starting from the bottom, 'd's starting from the top, muddled-up 'f's, and confused 'g' and 'q' tails).
Needless to say, if a student must struggle just to produce legible handwriting at any reasonable speed, he'd naturally going to dislike it. My guess is, some previous teacher, in a race to the finish lins, had decided to cut corners with the basics and move on to the 'important stuff'
I've managed to turn some students to enjoying handwriting a little more just by taking some time to teach them propper letter forms and efficient joins! You know, the unimportant stuff busy teachers haven't got time for.
Now as for history in simple English, you could try:
http://ogden.basic-english.org/ghos1.html
I'll warn you though: this book is full of typos, so you might want to edit it first. And since it is a little outdated, you might need to explain a few points to the students too.
As for grammar, no, the book isn't that easy. But as for vocabulary, it's very low level. It's based on Ogden's Basic English, and certainly has no literary pretensions.
You'd mentionned a range of levels also. Another option would be to choose selected approapriate passages from the KJV side-by-side with a paraphrase from the Bible in Basic English ()also based on the same 850 words of Ogden's Basic English. this could allow the student to choose to what extent he wishes to try to understand the KJV, or to just stick to the BBE.
It's available here:
http://www.o-bible.com/
And if you check:
http://ogden.basic-english.org/readings.html
You might find some useful stuff there too. But I'll warn you to be very selective: That site is full of typos.
And ifg you want help to produce your own written material, try:
http://www.online-utility.org/english/s ... helper.jsp
It includes Basic English along with other filtering options for text.
And you could try Simple English Wikipedia:
It hasn't got a formally defined form of English to be used, though, but it's likely to still be easier than standard English none-the-less:
http://simple.wikipedia.org/wiki/Main_Page