A New Jersey School Boards Association survey released Monday found 80 percent of school districts earlier this summer said they would have fewer teachers.
Almost half said they lost up to 5 percent of last year's staffing levels.
Most of the districts blamed state aid cuts for teaching staff reductions.
School Boards Association spokesman Frank Belluscio says many of the districts have been able to recall laid off employees after veteran teachers retired.
State pension officials say 5,435 teachers retired in July, more than double who retired a year ago. Some teachers have said they feared possible changes in pension rules.
