Unfortunately, blogger blog does not support posting articles to different pages. The new posts you are posting will be displayed on the homepage which is a static page. In order to make your posts appear on different tabs (looks like pages but not pages) you need to do the following steps:
1. Publish a new post.
2. Add keywords/labels to the new post
3. Go to layout in your blogger
4. Add Labels gadget above your blog posts body and save it.
5. If you have too many labels, you cn edit which labels to show. You can select the labels that are too frequent or label that has highest number of posts.
In this way, your blogger shows labels on your home page and when users click on a particular label, they will be redirected to posts that contain the same label.
Domain purchasing itself doesn't make your blogger into a website. You need to buy hosting as well. Hosting is a platform which hosts your new domain (ex: www.yourdomainname.com) and it requires some technical skill to redirect users from blogger to your new domain. If you simply buy a domain without hosting, your site will show error. And there are basically two different types of hosting:
1. Web Hosting
2. Wordpress Hosting
With webhosting you can migrate your blogger to any platform such as WorPress, Joomla, Drupal etc. After hosting this migration you need edit permalinks in your blogger and make your users redirect to your site.
While WordPress hosting exclusively supports wordpress and has good server speeds than webhosting. You need to migrate your blog to wordpress and do the same steps as above.
WordPress is most popular blogging platform and you easily migrate blogger with one clicks. Many hosting companies have separate hosting plans for WordPress. You can select according to your budget. the payment will be monthly, quarterly, yearly or for 3-6 years. Depending on the duration each company will provide certain amount of discounts as well. Higher the duration, higher is the discount. Basic plan may cost from 4,000 INR to 15,000 INR depending on the hosting site you choose. Some popular hosting sites are:
Each company provides different bandwidth, space, RAM, processor, monthly visits based on the plan you chose. Since you made your blog for school, I would recommend you to go for GoDaddy Wordpress basic hosting plan. This plan is quite economical when compared to others.
Dr. V. Shashikanth