A school website is best when it's transparent. Some schools want to create an online recruiting tool while hiding all relevant information for current or future parents. These schools might have apps, online school systems, mass emails or texts, login-protected pages, and social media accounts. Phil Collins might call this landscape a "Land of Confusion," and it's a result of generally poor leadership that grasps at anything bright and shiny. A good website can literally be all the things a school needs in one place, even if it's not entirely in one place.
Use the website to market to potential parents by showing what the school has to offer. Parents want to see the teachers and what's going on in the classrooms without having to join a Facebook page or download an app. A website can give a general idea of this, even if it's through links to newsletters or social media. However, a short biography and photo of every staff member should probably exist where parents can see them. Sure, you can try to get potential parents to sign up for a free e-book to get their emails, but turn the pop-up off for returning IP addresses and don't use the school's main page as a spam page. Write real content about the school, events, and what parents want to see happening--content that search engines see. Throwing this content on Facebook or Twitter is a waste of your time after the initial response, though it should be coordinated as a link from social media TO the main website.
Calendars and Updates
Current and future parents want to know what's happening at your school. All calendars and updated content should be on the main website to show this. If one teacher or coach uses some other system than what's on the main page, it needs to be linked or embeded. The website needs to be the one place every parent can see that shows every event and news item about the school. This really isn't difficult, but it takes some planning. For example, if the new volleyball coach prefers communicating via Facebook, then a link to the Facebook page needs to exist on the main website where the Volleyball heading is. If all of the best photos of the school are in Google Photos, then link out to Google Photos, adding some of those photos to the main website, perhaps. Nothing beats Google Calendar, but some schools will try to use other systems, often built in to clunky school administration programs. Don't bother. Set up one or more Google Calendars for your school and sports, add them to the main page, and be done with it.
You've got educational programs that require logins. Link to them. Google Classroom, online textbooks, gradebook, whatever. Your website could be your internal system if you want, but it's probably a better idea to use Google Suite for this heavy lifting. Even Microsoft Teams, if you're desperate. However, don't mistake Google Sites or whatever weird pages Microsoft creates as actual websites. Link to them and use them for their purpose, which is internal communication.
Social media, quite simply, should be used to direct current and future parents to your website. Write a snipit of an article that appears on the site. Add photos and then link to relevant pages on the site. Many schools do this in reverse, adding short descriptions to the website that link out to tons of social media content. However, if your website doesn't really have anything relevant there, then trying to send people to it doesn't help much. That's why you add lots of relevant, important, and transparent information to your school website from the start, and you keep it right there.