Yes, you are correct. Below is an excerpt from the attached IRS pdf.
D. New Employees: Safe Harbor for Variable Hour and Seasonal Employees
If an employer maintains a group health plan that would offer coverage to the employee only if the employee were determined to be a full-time employee, the employer may use both a measurement period of between three and 12 months (the same as allowed for ongoing employees) and an administrative period of up to 90 days for variable hour and seasonal employees. However, the measurement period and the administrative period combined may not extend beyond the last day of the first calendar month beginning on or after the one-year anniversary of the employee’s start date (totaling, at most, 13 months and a fraction of a month). These periods are described in greater detail below.
1. Initial Measurement Period and Associated Stability Period
For variable hour and seasonal employees, employers are permitted to determine whether the new employee is a full-time employee using an “initial measurement period” of between three and 12 months (as selected by the employer). The employer measures the hours of service completed by the new employee during the initial measurement period and determines whether the employee completed an average of 30 hours of service per week or more during this period. The stability period for such employees must be the same length as the stability period for ongoing employees. As in the case of a standard measurement period, if an employee is determined to be a full-time employee during the initial measurement period, the stability period must be a period of at least six consecutive calendar months that is no shorter in duration than the initial measurement period and that begins after the initial measurement period (and any associated administrative period).
If a new variable hour or seasonal employee is determined not to be a full-time employee during the initial measurement period, the employer is permitted to treat the employee as not a full-time employee during the stability period that follows the initial measurement period. This stability period for such employees must not be more than one month longer than the initial measurement period and, as explained below, must not exceed the remainder of the standard measurement period (plus any associated administrative period) in which the initial measurement period ends. In these circumstances, allowing a stability period to exceed the initial measurement period by one month is intended to give additional flexibility to employers that wish to use a 12-month stability period for new variable hour and seasonal employees and an administrative period that exceeds one month. To that end, such an employer could use an 11-month initial measurement period (in lieu of the 12-month.
An employee or related individual is not considered eligible for minimum essential coverage under the plan (and therefore may be eligible for a premium tax credit or cost-sharing reduction through an Exchange) during any period when coverage is not offered, including any measurement period or administrative period prior to when coverage takes effect.
In addition, here is an excerpt from http://www.irs.gov/irb/2014-9_IRB/ar05.html with regards to educational organizations.
Commenters also requested that employers that are educational organizations be prohibited from taking potential employment break periods into account in determining their expectations of future hours of service. For a description of the employment break period rule, see section VII.E.2 of this preamble. The final regulations clarify that educational organization employers cannot take into account the potential for, or likelihood of, an employment break period in determining their expectations of future hours of service.