No backpack? I know, I was just as shocked as you when I realized my son was the only one with a backpack. As it turns out, most preschools prefer your child not have a backpack due to limited storage space, according to Parenting. Basically, your child's teacher has no room for your backpack even if you did spend more on faster shipping because you only remembered to order supplies the Friday before school started.

Whether you unknowingly brought your child to school with a few extra "plus ones" seated comfortably on their scalp or not, the preschool will be decidedly unhappy if you introduce lice to the classroom. In fact, just to be safe, don't bring anything that's technically classified as a "parasite" to your child's preschool. It really doesn't make for a good first impression.

Bringing in foods which other children could be severely allergic to is a huge no-no for school. According to VeryWell, many classrooms are enforcing stricter rules on allergens, so it's best to check with your child's school on their food policy.

Yes, you read that correctly. A friend once told me about a parent (who shall remain nameless) bringing their kid to preschool with a diaper full of steaming sewage because, "she didn't want to change it and figured it was the teacher's job anyways." Seriously. Please don't bring hazardous material into preschool via your child's pants unless you want to get side eye from every teacher for the rest of the school year.

According to Parenting, your child's preschool teacher wants you to empty your kid's book bag of the previous day's contents. Even if you can't tell that the blob of green and red swirls are supposed to be a tree and apples (duh, so obvious), it will mean a lot to your child and their teacher if you show interest in their activities from their day at school. Just smile and nod when they tell you that square covered in glitter is an elephant.

There's never a good time for anyone to get sick, but take one for the team and keep your child home from school if they're ill. Melissa Mowry, author of One Mother to Another: This Is Just Between Us and former preschool teacher, told Scary Mommy that no preschool wants your kid to bring germs to school. Mowry also added that teachers are hip to sneaky tricks, saying, "don’t send your feverish kid in hyped up on Tylenol. You know we’re just gonna call you in 2 hours when it wears off." Point taken.

Though many preschools stave off potential zombie apocalypses on the regular by frequently using sanitizer, most teachers don't want your child to bring personal hand sanitizers to school, according to VeryWell. It sounds counter-intuitive since toddlers and young children are a virtual cesspool of germs that would make a truck-stop motel mattress look sanitary. But it turns out the reason is quite simple: if your kid has their own mini sanitizer, it's more difficult for an adult to supervise their use. So leave it to the professionals and try not to think about how much snot your kid has consumed today.

Unless your preschooler has a part-time job as a resort wear model for Salvatore Ferragamo, flip flops and open-toed shoes shouldn't be worn to class, according to TIME. Sure, it's much easier to slip a pair of sandals on your spirited sprout (read: tantruming toddler) than to use crocodile wrestling techniques to put on sneakers. Maybe that's how Crocs got their name.

Everyone has off days, weeks, months, or even years—*clap clap clap clap*—but when you start your child's day at school on a negative note, it can really set the tone for how they'll behave during class. According to Kids Health, an educational site from Nemours, bringing a bad attitude to school undermines a good relationship between child, teacher, and parent. If there really is a problem, then take a minute to schedule a meeting with your child's teacher or set aside time to listen to your child's concerns.

According to Reader's Digest, most teachers don't want your child to bring electronics to school. Preschoolers already have a hard enough time focusing their attention on something important, so digital distractions usually only make matters worse, especially in the classroom.

Allow me to paint you a picture. My son doesn't just love guacamole. He goes after these mushed up avocados harder than Guy Fieri ravaging a basket BBQ ribs on a trip down to Flavor Town. So I learned early on that I needed to pack more than one back-up shirt for my son's post-snack disaster. As it turns out, the experts at Today's Parent agree, as they noted, "come to school with extra sets of clothes in a labeled zip-top bag in case they have an accident." Trust me, it's better than driving home with a toddler who look like he got in a fight with the Slimer from Ghostbusters.