Book 5 covers word families all-alk, old-olt-oll, ild-ind, three-letterblends thr, shr, scr, str, spr, spl; qu words; and three sounds of -ed.
Level 6 covers vowel plus r: ar,or,er,ir, ur,wor,war;second sounds of ea;ie;igh;oo; dipthongs oi-oy and ou-ow;au-aw;ew-ui-ue-ou.
You only need the whole number books if your student catches on right away. If they need more practice, order the set that includes the half numbers as well. If a student does eight pages a day, they will go through 3 books/yr.