The NLRB holds for class actions
The National Labor Relations Board holds that individual employment agreements may not prevent employees from engaging in protected concerted activity in both union and nonunion environments.
The Board ruled in D.R. Horton that individual, as opposed to collectively bargained, arbitration agreements that are a condition of employment, may not bar collective action through both arbitral and judicial forums.
In contrast, most courts enforce arbitration agreements that foreclose class actions.See for example, the Fifth Circuit.
This article "The NLRB v. The Courts: Showdown Over the Right to Collective Action in Workplace Disputes" by Boston College Professors Stephanie M. Greene & Christine Neylon O'Brien sides with the NLRB’s interpretation. American Business Law Journal, Vol. 51, No. 4, 2014