We love this pattern kit from Lakeshore. The claim that they are indestructible, and while the beads and strings are very sturdy, I would recommend laminating the pattern cards before giving them to your kids. Patterning is a standard early childhood goal, and our kids need a lot of help working on building patterns. They love following pattern guides and trying to recreate them on their own.
I pour out the beads into shallow buckets so that they are easier to see and find. This also limits frustration for the students and helps keep the beads on the table.
String Beads Tip:
Tie a paper clip onto the end of the string to help keep the beads from falling right off the other side.