It’s senior slump time.

Like seasonal allergies, “senioritis” goes into attack mode around this time each year. Merriam-Webster defines it as: “an ebbing of motivation and effort by school seniors as evidenced by tardiness, absences, and lower grades.”

And BuzzFeed adds this: “The only known cure is a phenomenon known as graduation.”

Every year there are hundreds of cocky kids who mistakenly believe their college acceptances are ironclad.

Colleges vary tremendously in how they handle a “senior slump.” Some give warnings, some place students on academic probation and some actually reverse their decisions. Far more common than revocation is a warning letter, expressing disappointment, and asking for some explanation. Acceptance letters will usually state that the final acceptance is contingent on consistent performance.

Some students have adopted a very dangerous sense of teenage invulnerability. It usually starts out innocently enough with a missed assignment and then can devilishly detour into a full-blown case of senioritis. Many senior slackers are walking around with a sense of entitlement, “I worked really hard, I did my job, I got accepted to college, now it’s my time to take it easy.” Not so fast.

Roughly one-third of colleges revoke admissions each year, but most colleges are not likely to do so unless there is a dramatic decline; floating from a B to a C in a single course will not turn heads. but a former A Honor Roll student scraping by with C’s and D’s is a major red flag. Senioritis can be expensive, too. Underperformers can lose scholarships and financial aid packages.

It’s a cautionary tale and parents, high school administrators and even college admissions officers wish students would take it more seriously. With so many applicants and long waiting lists, colleges may be less willing to gamble on a student who has faltered.

Parents shouldn’t ignore any slide in grades or a lack of motivation. Start out by explaining the serious consequences that could occur, and encourage them to follow-through with the same dedication they had when they started their senior year.

Thankfully this condition doesn’t affect most students. Seth Allen, Vice President and Dean of Admissions and Financial Aid at Pomona College in Claremont, Calif., said, “It seems to me that the students who worry most about senioritis are, ironically, the students who can afford to let up a little to enjoy their many accomplishments and hard work.’’