Myth: Students hired only for the summer months are "seasonal workers," so even if they are going to be working at least 30 hours per week, your business isn't subject to the employer shared responsibility penalties if the students aren't offered group health coverage.
Busted: The penalties don't apply to an employer who does not offer group health coverage to seasonal workers immediately after hire, even if the seasonal worker is expected to work at least 30 hours per week when hired. The employer can use the "lookback method" and delay offering group health coverage until the seasonal worker has been employed an average of at least 30 hours per week for a full "measurement period." So being able to classify employees as "seasonal workers" allows an employer to postpone offering group health coverage to those employees without incurring penalties.
However, an employee is a "seasonal worker" only if the work the employee will be doing is specific to the season. Agricultural workers are seasonal workers because the work they are hired to do can't be done other than during the growing season. Retail employees hired for the holiday season are seasonal workers because they work they are hired to do only exists during the holiday season. If the work can't be done another time of the year, the work is seasonal - and so is the employee hired to do the work.
If your business hires students during the summer because that's when the students are available to work, and not because the work the students will do can only be done during the summer (by the students or anyone else), the students aren't "seasonal workers." Just because the students are only available to work during the summer doesn't make them "seasonal workers" - it's the time of year when the work has to be done that controls whether an employee is a "seasonal worker."
That said, your business is only required to offer coverage that will be effective after the student has been employed on a full-time basis for 90 days. If the student is employed for fewer than 90 days, there's no obligation to cover the student. And your business is only required to offer the coverage; if a student is covered by a parent's group health plan, the student may not sign up for your coverage.