Holidays mean a lot for many students. Adding holiday themed/deigned activities into classroom lessons can increase student engagement and class morale. Here are some resources for classroom teachers on Halloween, from decorating to integrating the holiday into course curriculum.
Pinterest - 222 of the Best Halloween Images/Activities
Teacher Vision - Halloween Worksheets and Resources
TeachHub - Halloween Activities for Any Grade
While Holiday lessons are engaging for most students, there are some that do not celebrate holidays as they may not fit with their beliefs. However, these students do not need to be excluded from these lessons. Here is a resource for providing alternative lessons that can still encourage participation and engagement without infringing on the students' beliefs. This falls along the same lines as differentiating instruction for each student's needs.
Lessons4Now - Students Who Don't Celebrate Holidays