Hi,
This is what i find and helped me a lot a wile ago. there where driver problems on the macbooks:
Begin by opening "Terminal," Apple's line command system application. You can find Terminal by opening Finder and clicking "Applications." Once in Applications, click on a folder labeled "Utilities," and then double-click on "Terminal." Or, use spotlight by holding the Command key and hitting the spacebar to open a search bar in the top right of you screen. Type "terminal" in the search bar and click on the Terminal application in the search results.
Once the Terminal window is open, enter the following command and hit enter.
sudo launchctl unload -w
/System/Library/LaunchDaemons/com.apple.discoveryd.plist
Enter your administrator password if you are prompted. This command will unload discoveryd. Now, to reload it, enter the following command and hit enter.
sudo launchctl load -w
/System/Library/LaunchDaemons/com.apple.discoveryd.plist
You may need to close and relaunch connected applications for this to take effect. If you still have no luck, you can try removing network configuration and preference files. Start by turning Wi-Fi off in the menu bar and opening the Finder window.
To open a search for a folder within Finder, hold the Command key, the Shift key, and the G key. When the search bar opens, enter the following phrase to get to the correct folder.
/Library/Preferences/SystemConfiguration/
Once in the folder, you need to find the following files and either delete them, or copy them into a backup folder somewhere else on your machine, or onto a removable drive. The main thing is making sure they are moved out of the system configuration folder.
com.apple.airport.preferences.plist
com.apple.network.identification.plist
com.apple.wifi.message-tracer.plist
NetworkInterfaces.plist
preferences.plist
After you have taken care of these files, reboot your machine and turn Wi-Fi back on from the menu bar. Your computer will then recreate these files which could solve some Wi-Fi problems.
If you are having trouble with specific websites, try flushing your DNS cachethrough terminal.
Hopefully this will solve your Wi-Fi problems and get you back online.